ACUTE CAFFEIN INTOXICATION. (continued 2)
Reading edition
October 6: 11.35 a. m., 7.8 cc 2 per cent caffein (0.2 gram per kilo) injected subcutaneously; 12 noon, reflexes increased markedly; 4.20 p. m., reflexes the same as at 12 noon.
October 7: 9 a. m., dead. Autopsy: Lungs congested; liver congested and fatty; spleen congested, kidney showed hemorrhagic spots; gastric mucosa necrotic; small portion of small intestine inflamed.
Guinea pig 69. White male. Weight, 585 grams. Diet, oats.
October 6: 11.40 a. m., 5.8 cc 2 per cent caffein injected subcutaneously; 12 noon, reflexes increased, but not as much as in No. 68; 4.20 p. m., guinea pig hypersensitive, reflexes increased more than at 12 noon.
October 7: 9 a. m., alive.
October 15: 9 a. m., found dead.
Guinea pig 61. Brown and black female. Weight, 330 grams. Diet, oats.
October 3: 4 p. m., 4 cc 2 per cent caffein (240 mg per kilo) injected subcutaneously; 5.30 p. m., reflexes increased; runs, but drags posterior extremities.
October 4: 8.50 a. m., found dead.
Guinea pig 62. White, yellow, and black female. Weight, 335 grams. Diet, oats.
October 3: 4.05 p. m., 4 cc 2 per cent caffein (238 mg per kilo) injected subcutaneously in the back; 5 p. m., convulsions; 5.20 p. m., convulsions, alternating with paralysis of anterior and posterior extremities.
October 4: 8.50 a. m., found dead.
Guinea pig 70. White and brown male. Weight, 545 grams. Diet, oats.
October 7: 3 p. m., 6.5 cc 2 per cent caffein (238 mg per kilo) aqueous solution injected subcutaneously; 3.50 p. m., reflexes increased.
October 9: 9 a. m., found dead.
Guinea pig 71. Brown and white male. Weight, 540 grams. Diet, oats.
October 7: 3 p. m., 6.5 cc 2 per cent caffein solution (0.24 gram per kilo) injected subcutaneously; 3.45 p. m., reflexes increased, tetanus.
October 9: 9 a. m., found dead.
Guinea pig 72. Brown and white male. Weight, 560 grams. Diet, oats.
October 7: 3 p. m., 6.5 cc 2 per cent caffein (0.232 gram per kilo) aqueous solution administered by subcutaneous injection; 3.35 p. m., reflexes increased.
October 10: found dead. Autopsy: Nos. 70, 71, 72 showed congestion of organs.
The reaction to caffein in the experiments of this series (C) showed considerable variation. The appearance of symptoms, as well as the final outcome of the experiments, differed markedly in a number of cases, notwithstanding the fact that the conditions were the same; thus the administration of 0.2 gram per kilo to guinea pigs, all of which received the same diet, induced no symptoms in two of the animals (Nos. 66 and 65), while marked symptoms were observed in the other four; in two of these the symptoms appeared in one hour and a quarter after injection, and in two others (Nos. 68 and 69), mild symptoms only appeared in 20 or 25 minutes. The last two were under observation for 4 hours longer, but there was no visible change in their condition. The duration of life in all of these guinea pigs, as indicated in the table, likewise varied. Two (Nos. 60 and 68) died during the night after they received caffein, one survived (No. 65), and three others (Nos. 57, 66, and 69) lived 2½, 5, and 9 days, respectively. Experiments with larger doses likewise showed differences in the behavior of these animals toward caffein, but they were not quite so marked. As shown in the table, symptoms appeared in from 35 minutes to 1.5 hours after injection. The duration of life was less than 1 day in two pigs, about twice as long in two others, and in one case between 2 and 3 days.
A comparison made with results obtained in the preceding series shows a striking difference in the resistance to caffein. As 2 decigrams per kilo proved more rapidly fatal to the guinea pig than the larger doses employed in the later experiments, this difference in the resistance to caffein may be due to several factors. As pointed out in the experiments on rabbits, age might be an important factor influencing the toxicity of caffein. Unfortunately, no accurate data were available on the age of the guinea pigs, but they were all apparently full grown, although they differed in weight considerably. The difference in their ages was in all probability not very great. Moreover, it will be observed that the resistance in series B and C differed in animals of approximately the same weight. This is evident on comparing experiments Nos. 20, 38, and 13 of series B with Nos. 65, 66, and 69 of the next series. Again, further inspection and analysis of these tables show no difference in the toxicity, although there may be considerable difference in the weight, from which it may be concluded that the animals were of about the same age or that this plays no part in the resistance to caffein in the guinea pig.
Diet is another factor which should be taken into consideration in this connection. The recent work of Hunt39 indicates that this may influence the resistance of animals to some poisons. Our experiments, however, fail to show any difference in the toxicity of the caffein in guinea pigs, whether fed oats, carrots, or both, for different results were obtained on the same diet, and there seemed to be little or no difference in the toxicity of caffein when the diet was different. Other explanations suggest themselves to account for the results obtained. Seasonal changes have been assigned by a number of investigators as a cause of variation in the resistance to drugs. According to Focke,24 frogs are more susceptible to digitalis in the spring than in the summer, while Moschkowitsch61 and Edmunds21 reported the very opposite results. Schmiedeberg's80 observations on strophantin in frogs were in harmony with those of Edmunds21 and Moschkowitsch.61 Similar results were reported with guinea pigs. Harrington's34 experiments indicate that stimulation of the vagus is less effective from October to January than from February to April, when they are also much more susceptible to operative procedure. Hunt found that the resistance of guinea pigs to aceto nitril is about twice as great in the summer months as it is in January and February.
Race might also be thought of as an important factor in this connection. Since the guinea pigs used at different seasons of the year were of several varieties, there is no reason to suppose, however, that the varieties experimented upon in the summer were more resistant than those used in the winter and spring. It is highly probable, therefore, that the greater resistance to caffein of the guinea pigs of series C than those of series B was due to seasonal variation.
Doses of 0.20 to 0.24 gram caffein per kilo weight, therefore, may be regarded as the minimum fatal dose for the guinea pig, depending upon the season. Since 0.2 gram per kilo proved to be rapidly fatal in series B, this quantity was perhaps not the minimum fatal dose for the guinea pig at the season during which the experiments were made. Additional tests with smaller doses were therefore carried out during February and March. The results are shown in series D.
Series D.
Guinea pig 49. Male. Weight, 510 grams. Diet, oats for 1 month previous to experiment.
March 17: 3 p. m., 4 cc 2 per cent caffein (0.16 gram per kilo) were injected subcutaneously; 4.40 p. m., reflexes increased; 5.40 p. m., no symptoms.
March 18: 9 a. m., found dead, died in less than 18 hours. Autopsy: Hemorrhage into abdominal cavity; liver and spleen unduly congested; intestines injected; hemorrhagic area at point of injection.
Guinea pig 40. Male. Weight, 630 grams. Diet, oats and carrots one week previous to injection.
February 12: 11 a. m., 5 cc 2 per cent caffein (0.158 gram per kilo) injected subcutaneously into back.
February 13: 1 p. m., still alive.
February 14: 9 a. m., found dead.
Guinea pig 45. Female. Weight, 435 grams. Diet, oats for about one month previous to injection.
March 17: 3 p. m., 3.5 cc of 2 per cent caffein injected subcutaneously in the back (0.160 gram per kilo); 4.35 p. m., no symptoms; 5.40 p m., no symptoms.
Guinea pig 39. Male. Weight, 820 grams. Diet, oats and carrots.
February 12: 11 a. m., 6 cc (0.15 gram per kilo) 2 per cent caffein injected subcutaneously in back.
February 14: 9 a. m., alive; seemed to be in good condition; found dead at 1 p. m.
Guinea pig 41. Weight, 660 grams. Diet, oats and carrots one week previous to injection.
February 12: 11 a. m., 5 cc (0.15 gram per kilo) 2 per cent caffein injected subcutaneously.
February 14: 2 p. m., pig alive; apparently normal.
February 18: Guinea pig still alive and apparently in good condition.
Guinea pig 46. Female. Weight, 470 grams. Diet, oats about one month previous to experiment.
March 17: 3.15 p. m., 4 cc (0.170 gram per kilo) 2 per cent caffein injected into back subcutaneously; 4.35 p. m., reflexes increased, tremors on handling marked; 5.40 p. m., no change, symptoms about as before.
March 18: 2.30 p. m., no symptoms.
The experiments of this series (D) likewise showed a considerable difference in the resistance of the individual guinea pigs. Nos. 41, 45, and 46 survived; the rest of the pigs died within 18 hours to 2 days after the administration of caffein. Since an autopsy was held on one only, it is impossible to assign a cause for the variation in the toxicity of caffein in these guinea gigs, as the diet and the other conditions under which the experiments were conducted were the same. It was found in the experiments on cats and rabbits that the presence of morbid processes tends to increase the toxicity of caffein. The observations of Ophüls66 are of interest in this connection. He found spontaneous lesions of the kidney and liver in a large proportion of guinea pigs examined. The greater susceptibility to caffein of guinea pigs Nos. 39, 40, 49, is probably due therefore to some pathological change which increased its toxicity. About 0.2 to 0.24 gram per kilo may therefore be regarded as the minimum lethal dose for the normal guinea pig when caffein is introduced subcutaneously, the minimum toxic dose being about 150-160 mg per kilo.
Experiments were also conducted to determine the largest dose which does not produce any visible effects. In a number of tests with from 100 to 120 mg caffein per kilo (series E, see Table 6, p. 51) no manifestation of nervous or muscular disturbance nor any departure from the normal in respiratory activity was observed. Such quantities may be regarded as the largest doses which are surely safe for these animals. It is quite possible, therefore, that the greater variation in the toxicity of caffein observed in these experiments is due to morbid conditions. Moreover, there is some evidence that caffein increases the toxicity of certain poisons, as shown by Hale33 for acetanilid. Is it not possible that caffein may similarly be affected by poisons circulating within the body? Indeed the recent work of Loeb23 makes this supposition highly probable. This investigator found that caffein and adrenalin injected together produce myocarditis in the rabbit. It is conceivable that the combined action of caffein and some preexisting poison may cause changes which terminate in the death of the animal. The delayed death of guinea pigs after the administration of caffein observed in this and other series may probably be accounted for in this way.
Experiment 57 lends some support to this view. The condition of the kidneys and the presence of a severe gastro-enteritis are sufficient to account for the death of this case. Again the frequent association of gastro-enteritis and congestion of the organs in caffein intoxication found in different animals makes it highly probable that these lesions were caused by caffein.
INJECTION INTO THE PERITONEAL CAVITY.
The experiments were carried out with different doses. All the guinea pigs in this series were kept on a uniform diet, consisting of oats. Most of them were of average size and there were no wide variations in their weights. The experiments of series A with the smallest doses were conducted in March and April; all the other experiments it will be noticed were made in October.
Series A.
Guinea pig 41. Weight, 700 grams. Diet, oats.
April 1: 3.30 p. m., 4.5 cc 2 per cent caffein (130 mg per kilo) injected into peritoneal cavity. 5.35 p. m., symptoms present but no tetanus.
April 2: Found dead about 2 p. m., duration of life about 22 hours. Autopsy: Subcutaneous hemorrhage at the point of inoculation; serious exudate on visceral and parietal peritoneum with marked inflammation of peritoneum; portions of intestines showed slight enteritis.
Guinea pig 49. Male. Weight, 370 grams. Diet, oats.
April 1: 3.15 p. m., 2.5 cc 2 per cent caffein (135 mg per kilo) injected into the peritoneal cavity; 5.30 p. m., symptoms present; reflexes increased, but no tetanus. Guinea pig survived.
Guinea pig 47. Female. Weight, 550 grams. Diet, oats since about February 4.
March 17: 3.30 p. m., 3.5 cc 2 per cent caffein (127 mg per kilo) injected into peritoneal cavity; 4.35 p. m., increased irritability present, but not marked; 5.40 p. m., symptoms about the same as before.
March 18: 2.30 p. m., condition good; no symptoms. Survived.
Guinea pig 50. Female. Weight, 290 grams. Diet, oats.
April 1: 3.30 p. m., 2 cc 2 per cent caffein (138 mg per kilo) injected into peritoneal cavity; 5.35 p. m., symptoms present; reflexes much increased, but no tetanus. Survived.
Series B.
Guinea pig 51. Yellow female. Weight, 415 grams.
October 1: 9.50 a. m., 3 cc (144 mg per kilo) 2 per cent caffein injected into peritoneal cavity; 4.30 p. m., no symptoms, although under observation all day.
October 3: 2 p. m., alive.
Guinea pig 52. White male. Weight, 450 grams.
October 1: 9.45 a. m., 3.5 cc, 2 per cent caffein (155 mg per kilo), injected into peritoneal cavity; 4.30 p. m., no symptoms developed since injection.
October 3: 2 p. m., alive.
Guinea pig 58. Brown and white male. Weight, 490 grams.
October 1: 9.45 a. m., 4 cc, 2 per cent caffein (163 mg per kilo), injected into peritoneal cavity; 4.30 p. m., no symptoms developed since injection.
October 3: 2 p. m., alive.
October 8: Found dead. Autopsy: Congestion of lungs, spleen, liver, kidneys, and small intestines.
Series C.
Guinea pig 59. Gray and white. Weight, 375 grams. Diet, oats.
October 3: 2 p. m., 3.75 cc (0.2 gram per kilo) injected into peritoneal cavity; 2.15 p. m., reflexes increased but not markedly; 4 p. m., reflexes still more increased; no other symptoms; 5.30 p. m., no symptoms.
October 4: 8.50 a. m., guinea pig alive and active.
Guinea pig 58. Brown and white. Weight, 380 grams. Diet, oats.
October 3: 2 p. m., 3.8 cc caffein (0.2 gram per kilo), 2 per cent solution, injected into peritoneal cavity; 2.10 p. m., hind legs extended, then tetanus; attack lasted a few seconds, after which pig raised himself on his legs, but reflexes remained much exaggerated; 4 p. m. to 5.30 p. m., no symptoms of caffein intoxication.
October 4: 8.50 a. m., guinea pig alive and active.
Guinea pig 56. Gray and white male. Weight, 440 grams. Diet, oats.
October 1: 11.30 a. m., received 4.6 cc of 2 per cent caffein solution (0.2 gram per kilo) into abdominal cavity; 11.45 a. m., stiffness and rigidity of posterior extremities, reflexes increased; 12.30 p. m., hind legs paralyzed, reflexes increased; 4.35 p. m., no symptoms, guinea pig in good condition.
October 3: Still alive in good condition.
October 14: Died. Autopsy: Anterior lobe of right lung hepatized. Small portion of small intestine edematous. Other organs normal.
Guinea pig 55. White and yellow male. Weight, 690 grams. Diet, oats.
October 1: 11.30 a. m., received 6.5 cc of 2 per cent solution caffein (188 mg per kilo) into peritoneal cavity; 11.40 a. m., stiffness in all extremities, reflexes markedly increased; 12.30 p. m., reflexes increased, anterior and posterior extremities paralyzed; 3 p. m., found dead.
Series D.
Guinea pig 67. Gray and yellow male. Weight, 330 grams. Diet, oats.
October 5: 11.25 a. m., 4 cc of 2 per cent caffein injected into peritoneal cavity (240 mg per kilo); 11.30 a. m., tetanus—survived, convulsions off and on. Death at 2.55 p. m. Autopsy: Severe gastroenteritis; kidney petechiated; congestion of lungs and liver.
Guinea pig 63. Gray and white male. Weight, 340 grams. Diet, oats.
October 5: 11.20 a. m., 4 cc of 2 per cent caffein (235 mg per kilo) injected into peritoneal cavity.
October 14: Alive and in good condition.
Guinea pig 64. Brown and black female. Weight, 305 grams.
October 5: 11.35 a. m., 3.8 cc 2 per cent solution caffein (250 mg per kilo) injected into peritoneal cavity; 11.40 a. m., tetanus—survived, convulsions off and on, died at 4.15 p. m. Autopsy: Findings exactly the same as in No. 67.
Examination of the results of the experiments by intraperitoneal injections showed that 0.2 gram caffein per kilo was toxic in two guinea pigs (Nos. 59 and 58). Severe symptoms were observed within 15 minutes in No. 56 and within one hour in No. 55 after the administration of approximately the same dose of caffein. One of these died within three and one-half hours; the other, No. 56, made a good recovery from the acute effects. This amount of caffein may be regarded, therefore, as the minimum toxic dose for the guinea pig when injected into the peritoneal cavity. This is corroborated by the experiments of series B in which smaller doses failed to show any muscular, nervous, or respiratory symptoms, nor were there any after effects noticed, as all of them survived and were kept under observation for some time. The guinea pigs of series A, however, seem to contradict these results. It will be remarked that appreciably smaller doses induced symptoms in all of them, and one case terminated fatally. The seasonal variation, as already pointed out, is in all probability likewise responsible for the difference in the resistance between the guinea pigs of series A and B. Tests were made also to determine the minimum fatal dose. For this purpose the experiments of series D were performed. The resistance of No. 63 in this series is quite striking. We are unable to explain such a discrepancy in the results obtained under practically uniform conditions. The minimum fatal dose of caffein, when injected into the peritoneal cavity, is therefore about 240 to 250 milligrams per kilo. These amounts, it will be observed, were rapidly fatal, in striking contrast to the results obtained when such doses were injected subcutaneously. This is probably due to a better absorption from the peritoneal cavity than from the subcutaneous tissues.
ADMINISTRATION BY MOUTH.
All the guinea pigs in these experiments were kept on a diet of hay and oats and were of large size. The tests were made with different doses of caffein in order to determine the limits of toxicity when the drug was administered by mouth.
Guinea pig 129. White and black male. Weight, 855 grams. Diet, oats and hay.
June 6: 2.20 p. m., 12 cc of 2 per cent caffein (0.28 gram per kilo) by mouth; 3 p. m., reflexes increased; 5 p. m., reflexes still more increased; no other symptoms.
June 7: 9 a. m., found dead; guinea pig passed 75 cc urine, which was almost colorless. Autopsy: Heart and blood vessels injected; lungs congested; small intestines congested; other organs apparently normal.
Guinea pig 130. Black and brown male. Weight, 800 grams. Diet, oats and hay.
June 6: 2.30 p. m., 12 cc of 2 per cent caffein (0.3 gram per kilo) administered by mouth; 3 p. m., reflexes increased; 5 p. m., increase of reflexes greater than at 3 p. m.
June 7: 9 a. m., found dead; only a few cubic centimeters of urine passed since 4 p. m. Autopsy: Heart and blood vessels injected; lungs congested; small intestines congested slightly.
Guinea pig 181. White and yellow male. Weight, 860 grams. Diet, oats and hay.
June 6: 2.40 p. m., 12 cc 2 per cent caffein administered by mouth; 3 p. m., reflexes increased; 5 p. m., reflexes still more marked.
June 7: 9 a. m., found dead, pig passed about 5 cc urine since 4 p. m. of previous day. Autopsy: Same as in No. 130.
Guinea pig 136. White and black male. Weight, 1,000 grams. Diet, oats and hay.
June 9: 4 p. m., 7.5 cc 2 per cent caffein solution injected subcutaneously into the back; 4.50 p. m., reflexes increased.
June 10: 9.30 a. m., more sensitive than normal guinea pigs, but reflexes not quite so marked as at 5 p. m. previous day, about 15 cc urine passed since caffein was injected, reduction of Fehling's solution considerable, no albumin.
June 13: Alive and in good condition. Appetite good. (Note.—Parallel test with urine from two guinea pigs which did not receive caffein failed to show reduction of Fehling's solution.)
Guinea pig 137. White and brown male. Weight, 925 grams. Diet, oats and hay.
June 9: 4 p. m., 7 cc 2 per cent solution caffein injected subcutaneously; 4.50 p. m., reflexes increased.
June 10: Reflexes less marked than at 5 p. m. previous day, but is more sensitive than normal guinea pig, about 10 cc urine passed since injection of caffein, moderate amount of reduction of Fehling's solution.
June 13: Guinea pig alive, appetite good, condition good.
June 16: 9 a. m., found dead.
Guinea pig 135. White and black male. Weight, 955 grams. Diet, hay and oats.
June 9: 3 p. m., 7.5 cc 2 per cent caffein solution given by mouth through stomach tube; 4.50 p. m., reflexes increased.
June 10: Reflexes less than on previous day and less marked than in No. 136, a few cubic centimeters dirty brown urine collected but could not be tested for reduction.
June 13: Condition good, appetite good.
June 16: 9 a. m., found dead.
Guinea pig 134. White and brown male. Weight, 740 grams. Diet, hay and oats.
June 9: 2.55 p. m., 6 cc warm 2 per cent caffein solution given by mouth through stomach tube; 4.50 p. m., reflexes increased.
June 10: 9.30 a. m., reflexes much less than day before, increase slight, a few cubic centimeters of urine passed since injection of caffein, looked brown and dirty, could not be tested for reducing substances.
June 13: Guinea pig alive, appetite good, condition good.
June 14: 9 a. m., found dead.
Guinea pig 128. White and black male. Weight, 1,075 grams. Diet, hay and oats.
June 7: 10 a. m., 11 cc 2 per cent caffein by mouth through stomach tube; 11.10 a. m., no symptoms, no urine passed; 1 p. m., increased reflexes, about 15 cc (estimated) urine passed; 4 p. m., reflexes increased, still more urine passed (about 20 cc); 4.50 p. m., tetanus, frequent attacks, then paralysis and death at 4.58 p. m. Autopsy: Lungs congested; blood vessels of heart injected; intestines slightly congested; fatty liver.
Guinea pig 126. White and gray male. Weight, 980 grams. Diet, oats and hay.
June 7: 9.40 a. m., 9.8 cc 2 per cent caffein given by mouth through stomach tube; 10 a. m., no symptoms; 11.10 a. m., no urine passed, reflexes increased; 1 p. m., more sensitive than before; 4 p. m., increase of reflexes more marked, no urine passed; 4.45 p. m., about 15 cc urine collected; 5 p. m., no change.
June 8: 9 a. m., reflexes about the same as 5 p. m. previous day, no urine passed since 4.45 p. m. previous day, considerable reduction of Fehling's solution, much more than urine of guinea pig No. 127; 11.05 a. m., convulsions; 12 noon, still alive and stretched out on abdomen; died at 1 p. m. Autopsy: Lungs badly congested; heart and blood vessels injected; blood vessels of kidney and of small intestines injected; liver engorged with blood; a few necrotic spots in stomach.
Guinea pig 127. White, black, and brown male. Weight, 760 grams. Diet, oats and hay.
June 7: 9.50 a. m., 7.6 cc 2 per cent caffein by mouth through stomach tube; 10 a. m., no symptoms; 11.10 a. m., reflexes increased, no urine passed; 1 p. m., very sensitive; 4 p. m., sensitiveness increased, about 20 cc urine passed; 5 p. m., no change.
June 8: 9 a. m., reflexes about the same as 5 p. m. previous day; 9.30 a. m., guinea pig passed 30 cc urine since he received caffein, urine showed a moderate amount of reduction; 12 noon, convulsions; died at 2.30 p. m. Autopsy: Lungs congested; blood vessels of heart and of intestines injected; numerous necrotic spots in stomach; other organs apparently normal.
Examination of the protocols shows that the absorption of caffein from the gastro-intestinal canal was quite rapid, symptoms having been observed as early as 20 minutes after its introduction. The duration of life, it will be remarked, varied with the size of the dose. When approximately 3 decigrams per kilo were fed, all the animals died in the night. They lived, therefore, less than 18 hours. Two decigrams per kilo were likewise fatal, but the duration of life was longer. To decide whether or not this is the smallest fatal dose, smaller amounts were fed. It seemed at first that about 150 mg per kilo was the smallest toxic dose, and about 200 mg per kilo the minimum fatal dose. Macroscopic examination of the organs, however, threw some doubt on this supposition, for well-marked lesions were noticed in all of the guinea pigs which received 0.2 gram per kilo. It is quite possible, therefore, that the minimum fatal dose may be somewhat higher, as we have reason to believe that, at least in some pathologic conditions, the susceptibility to caffein is increased. The presence of fatty changes in the liver of No. 128 and the rapid death in this case lends especial support to this view. Hence, the minimum fatal dose is probably greater than 0.2 gram per kilo for the normal guinea pig. The doses employed for the tests on guinea pigs Nos. 129, 130, and 131 may be considered therefore the minimum fatal dose for these animals. It will be also remarked that macroscopical examination of the organs of these animals failed to reveal the presence of severe lesions. That the minimum toxic dose is probably much smaller than 0.28 gram per kilo is indicated by the experiments on guinea pigs Nos. 135 and 134, in which 0.15 gram caffein per kilo induced mild symptoms in from two to three hours. Both of these, however, and also No. 137 died four to six days after the drug was fed. As already pointed out, caffein may be a factor in the delayed death of guinea pigs which received moderate doses of it. That this supposition may also be true for guinea pigs Nos. 134, 135, and 137 is indeed made probable by the observation that after moderate amounts of caffein symptoms may persist in the guinea pig for about 24 hours, and also by the fact that the secretion of urine in these animals was very scanty, as shown in the preceding record of the experiments; this means slow elimination of caffein and its products of decomposition. It is conceivable that the presence of toxic amounts of caffein in the body for a considerable length of time would induce changes that ultimately lead to the death of the animal or that morbid processes are set up by the combined action of caffein and some preexisting poison. Since some guinea pigs, however, survived the doses indicated, it is more probable that such changes would be brought about by caffein in the presence of a preexisting poison. The death of these pigs, and also of No. 137 several days later, is difficult to account for on any other theory than the one suggested. Were it not for the fact that controls, that is, animals of the same lot which had not received caffein survived all of the experimental animals, changed conditions of environment or accident might be considered the cause of death in the guinea pigs of the last series.
Table 6.—Subcutaneous injection of guinea pigs.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms inDuration of life. Diet. Month. Remarks.
Grams. Mg.
18 500 0.300 2 minutes2 hours 40 minutes CarrotsMarchFemale.
15 548 .29030 minutes Oats do. Do.
14 442 .360 15 minutes do. do. do. Do.
SERIES B.
20 497 0.2002 hours 20 minutes3 hours 30 minutes OatsAprilFemale.
38 570 .210 25 minutes2 hours 15 minutes CarrotsFebruaryMale.
37 820 .2001 hour 25 minutesLess than 18 hoursCarrots and oats. do. Do.
13 618 .19425 hoursOatsMarchFemale.
36 850 .200 1 hour 30 minutes 18 hoursCarrots and oats.FebruaryMale.
SERIES C.
66 510 0.200None5 daysOatsOctoberMale.
65 510 .200 do.Survived do. do. do.
60 320 .2191 hour 15 minutesWithin 18 hours do. do.Female.
57 350 .200 do.About 2½ days do. do. Do.
68 785 .200 25 minutesLess than 22 hours do. do.Male.
69 585 .200 20 minutes9 days do. do. Do.
61 330 .2401 hour 30 minutesLess than 24 hours do. do.Female.
62 335 .2381 hour do. do. do. Do.
70 545 .238 50 minutesAbout 2 days do. do.Male.
71 540 .240 45 minutes do. do. do. Do.
72 560 .232 35 minutesAbout 3 days do. do. Do.
SERIES D.
49 510 0.1601 hour 40 minutesLess than 18 hoursOatsMarchMale.
40 630 .158 Less than 2 daysOats and carrots.February Do.
45 435 .160 None SurvivedOatsMarchFemale.
39 820 .150 2 daysOats and carrots.FebruaryMale.
41 660 .150 Survived do. do.
46 470 .1701 hour 20 minutes do.Oats (?)MarchFemale.
SERIES E.
19 556 0.100Survived OatsApril
42 490 .120 None do. do.February
43 430 .116 do. do. do. do.
44 535 .112 do. do. do. do.
97 330 .100 do. do. do.November
98 520 .100 do.About 3 days Carrots do.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
18 500 0.300 2 minutes
15 548 .290
14 442 .360 15 minutes
Number of pig.Duration of life. Diet. Month. Remarks.
182 hours 40 minutes CarrotsMarchFemale.
1530 minutes Oats do. Do.
14 do. do. do. Do.
SERIES B.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
20 497 0.2002 hours 20 minutes
38 570 .210 25 minutes
37 820 .2001 hour 25 minutes
13 618 .19425 hours
36 850 .200 1 hour 30 minutes
Number of pig.Duration of life. Diet. Month. Remarks.
203 hours 30 minutes OatsAprilFemale.
382 hours 15 minutes CarrotsFebruaryMale.
37Less than 18 hoursCarrots and oats. do. Do.
13OatsMarchFemale.
36 18 hoursCarrots and oats.FebruaryMale.
SERIES C.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
66 510 0.200None
65 510 .200 do.
60 320 .2191 hour 15 minutes
57 350 .200 do.
68 785 .200 25 minutes
69 585 .200 20 minutes
61 330 .2401 hour 30 minutes
62 335 .2381 hour
70 545 .238 50 minutes
71 540 .240 45 minutes
72 560 .232 35 minutes
Number of pig.Duration of life. Diet. Month. Remarks.
665 daysOatsOctoberMale.
65Survived do. do. do.
60Within 18 hours do. do.Female.
57About 2½ days do. do. Do.
68Less than 22 hours do. do.Male.
699 days do. do. Do.
61Less than 24 hours do. do.Female.
62 do. do. do. Do.
70About 2 days do. do.Male.
71 do. do. do. Do.
72About 3 days do. do. Do.
SERIES D.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
49 510 0.1601 hour 40 minutes
40 630 .158
45 435 .160 None
39 820 .150
41 660 .150
46 470 .1701 hour 20 minutes
Number of pig.Duration of life. Diet. Month. Remarks.
49Less than 18 hoursOatsMarchMale.
40 Less than 2 daysOats and carrots.February Do.
45 SurvivedOatsMarchFemale.
39 2 daysOats and carrots.FebruaryMale.
41 Survived do. do.
46 do.Oats (?)MarchFemale.
SERIES E.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
19 556 0.100
42 490 .120 None
43 430 .116 do.
44 535 .112 do.
97 330 .100 do.
98 520 .100 do.
Number of pig.Duration of life. Diet. Month. Remarks.
19Survived OatsApril
42 do. do.February
43 do. do. do.
44 do. do. do.
97 do. do.November
98About 3 days Carrots do.
Table 7.—Injection into peritoneal cavity; guinea pigs.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms inDuration of life. Diet. Month. Remarks.
Grams. Mg.
41 700 0.1302 hours 15 minutes22 hoursOatsAprilMale.
49 370 .1352 hoursSurvived do. do. Do.
47 550 .1271 hour do. do.MarchFemale.
50 290 .1382 hours do. do.April Do.
SERIES B.
51 415 0.144 NoneSurvivedOatsOctoberFemale.
52 450 .155 do. do. do. do.Male.
53 490 .163 do. do. do. do. Do.
SERIES C.
59 375 0.200 15 minutesSurvivedOatsOctoberGray and white.
58 380 .200 10 minutes do. do. do.
56 440 .200 15 minutes14 days do. do.Male.
55 690 .188 1 hour3 hours 30 minutes do. do. Do.
SERIES D.
67 330 0.240 5 minutes30 minutesOatsOctoberMale.
63 340 .235Survived do. do. Do.
64 305 .250 25 minutes4 hours 40 minutes do. do.Female.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
41 700 0.1302 hours 15 minutes
49 370 .1352 hours
47 550 .1271 hour
50 290 .1382 hours
Number of pig.Duration of life. Diet. Month. Remarks.
4122 hoursOatsAprilMale.
49Survived do. do. Do.
47 do. do.MarchFemale.
50 do. do.April Do.
SERIES B.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
51 415 0.144 None
52 450 .155 do.
53 490 .163 do.
Number of pig.Duration of life. Diet. Month. Remarks.
51SurvivedOatsOctoberFemale.
52 do. do. do.Male.
53 do. do. do. Do.
SERIES C.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
59 375 0.200 15 minutes
58 380 .200 10 minutes
56 440 .200 15 minutes
55 690 .188 1 hour
Number of pig.Duration of life. Diet. Month. Remarks.
59SurvivedOatsOctoberGray and white.
58 do. do. do.
SERIES D.
5614 days do. do.Male.
553 hours 30 minutes do. do. Do.
SERIES D.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
67 330 0.240 5 minutes
63 340 .235
64 305 .250 25 minutes
Number of pig.Duration of life. Diet. Month. Remarks.
6730 minutesOatsOctoberMale.
63Survived do. do. Do.
644 hours 40 minutes do. do.Female.
Table 8.—Caffein by mouth; guinea pigs.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms in
Grams. Mg.
129 855 0.28040 minutes
130 800 .30030 minutes
131 860 .28020 minutes
135 955 .1501 hour 50 minutes
134 740 .1603 hours
1137 925 .15050 minutes
1136 1,000 .150 do.
126 980 .20020 minutes
127 760 .2001 hour
128 1,075 .2003 hours
Number of pig.Duration of life. Diet. Month. Remarks.
129Less than 8 hoursHay and oatsJuneMale.
130Less than 18 hours do. do. Do.
131 do. do. do. Do.
1356 days do. do. Do.
1344 days do. do. Do.
11376 days do. do. Do.
1136Survived do. do. Do.
12627 hours do. do. Do.
12728 hours do. do. Do.
1287 hours do. do. Do.
1 Subcutaneous injection for comparison.
SERIES A.
Number of pig. Weight.Caffein per kiloAppearance of symptoms inDuration of life. Diet. Month. Remarks.
Grams. Mg.
129 855 0.28040 minutesLess than 8 hoursHay and oatsJuneMale.
130 800 .30030 minutesLess than 18 hours do. do. Do.
131 860 .28020 minutes do. do. do. Do.
135 955 .1501 hour 50 minutes6 days do. do. Do.
134 740 .1603 hours4 days do. do. Do.
1137 925 .15050 minutes6 days do. do. Do.
1136 1,000 .150 do.Survived do. do. Do.
126 980 .20020 minutes27 hours do. do. Do.
127 760 .2001 hour28 hours do. do. Do.
128 1,075 .2003 hours7 hours do. do. Do.
1 Subcutaneous injection for comparison.
SUMMARY.
A survey of the results obtained in experiments on guinea pigs shows that the mode of introduction of caffein exerts but little influence on its toxicity. On careful analysis it will be observed that the rate of absorption after the administration of caffein by mouth, subcutaneously, or intraperitoneally is about the same for the time of appearance of symptoms. The persistence of the symptoms of caffein intoxication observed in these experiments for 24 hours after administration points to slow elimination, which may be expected, owing to the fact that the guinea pigs passed but little urine and caffein is not diuretic for these animals. The prolonged presence of caffein in the body probably exerts a harmful influence or after effect, which may account for the delayed death of some animals many days after a single dose of caffein was given. Among the factors which undoubtedly influence toxicity, season should be considered, while the presence of a diseased condition undoubtedly tends to decrease the resistance of the guinea pig to caffein. Diet was without any influence on the toxicity of the single dose of caffein.
EXPERIMENTS ON CATS.
These experiments were performed on well-fed animals which were kept under observation for several days before the tests with caffein were made. The diet consisted of meat exclusively. In some cases the urine was examined for albumin and sugar before caffein was given. No tests with caffein were made if large amounts of albumin were found. It may be remarked that sugar was never found in cats before the administration of caffein, but that considerable amounts of it were found in some cases after it was given. Studies by various modes of administration were made, by subcutaneous injection, intraperitoneally, or by mouth. Attention was also directed to the resistance to caffein in young cats, several experiments on kittens being made with this object in view.
SUBCUTANEOUS INJECTION.
Rost stated that caffein is eliminated in the urine unchanged after its introduction into the body and that the amounts found varied with different species of animals. In the rabbit the amount eliminated was about 21 per cent; in the dog about 8 per cent; and in the cat somewhat less than 2.5 per cent. It would appear, therefore, that the cat decomposes caffein more readily than the rabbit or dog; its resistance consequently ought to be greater than that of the other animals. Moderately large doses were accordingly employed in the preliminary experiments (series A), but the results obtained, as shown in the protocols, indicated that caffein is fully as toxic for the cat as for the rabbit or dog. The doses were then decreased and experiments were performed in order to ascertain the smallest toxic as well as the smallest fatal dose.
Series A.
Three decigrams of caffein per kilo were administered in these experiments. The results are shown in the following protocols:
Cat 4. Black and white. Weight, 1,440 grams.
May 26: 10.05 a. m., 22 cc 2 per cent caffein (0.3 gram per kilo) injected subcutaneously; 11.10 a. m., copious salivation, cat irritable, muscular stiffness present, but no tetanus; 11.45 a. m., cat restless, convulsions, attacks of short duration, no paralysis observed after the convulsions, pupils dilated; 4.45 p. m., cat quiet, slight paralysis present.
May 27: Cat exhausted.
May 28: Found dead.
Cat 5. Black and white male. Weight, 1,396 grams.
June 3: 10 a. m. 21 cc of 2 per cent caffein (0.3 gram per kilo) injected subcutaneously; 12 noon, found dead.
Although there was considerable difference in the duration of life following the injection of the same dose of caffein per kilo, the final outcome was the same, as both cats died from the effects of the drug. One died within 2 hours and the other lived more than 30 hours after its administration. Three decigrams of caffein per kilo is, therefore, surely fatal to these animals. Tests made with smaller doses are shown in the following experiments:
Series B.
In these experiments the doses employed ranged between 0.20 and 0.25 gram caffein per kilo.
Cat 3. Black and white female. Weight, 2,854 grams. Well fed.
June 4: 10.30 a. m., 35 cc 2 per cent caffein (0.25 gram per kilo) injected subcutaneously; 11 a. m., found dead.
Cat 6. Black and white. Weight, 1,645 grams.
June 3: 20 cc 2 per cent caffein (0.243 gram per kilo) injected subcutaneously at 3 p. m., cat grew very irritable in a few minutes; about 4 p. m. reflexes decidedly increased; 5 p. m., cat paralyzed.
June 4: Cat found dead.
Cat 8. Weight, 1,735 grams.
October 7: 4 p. m., 22 cc 2 per cent caffein (0.25 gram per kilo) injected subcutaneously in the back; 4.30 p. m., cat irritable, salivation profuse, convulsions; died at 5.30 p. m.; no urine passed after caffein was given.
Cat 9. Weight, 1,960 grams.
October 7: 3.45 p. m., 25 cc 2 per cent caffein (0.25 gram per kilo) injected subcutaneously in the back; 4.45 p. m., cat very irritable, repeated attacks of convulsions, salivation copious; died at 5.30 p. m.; cat did not urinate after injection of caffein.
Cat 12. Striped kitten. Weight, 1,185 grams.
October 9: Urine examined, no albumin, no sugar; 1.45 p. m., 12 cc 2 per cent caffein administered; 5 p. m., cat alive, no symptoms except salivation and general irritability.
October 10: 10.30 a. m., found dead. About 15 cc urine collected, but no examination made.
Cat 14. Black. Weight, 1,855 grams.
October 8: 1.40 p. m., 18.5 cc 2 per cent caffein (0.2 gram per kilo); 3 p. m., cat became restless about 10 minutes after caffein was injected; cried persistently and moved about in cage, no convulsions, cat urinated about 15 cc, cat defecated.
October 9: 9 a. m., cat found dead in cage. Urine gave very heavy reduction of Fehling's solution (much more than was obtained from urine of rabbits); 20 cc urine analyzed contained 4.65 per cent sugar. Autopsy: Lungs deeply congested; liver marked fatty infiltration and degeneration; spleen normal; kidneys pale and anemic; intestines normal; stomach normal.
Cat 15. Striped. Weight, 2,145 grams.
October 8: 2 p. m., 22 cc (0.2 gram per kilo) 2 per cent caffein injected subcutaneously; 2.30 p. m., cat irritable, restless, trying to get out of cage, crying persistently; 2.40, convulsions lasting about two minutes, then cat raised itself and made attempts to get out of cage, no salivation, cat urinated about 10 cc and defecated.
October 9: 9 a. m., cat found dead in cage, about 10 cc of urine contained enormous quantities of sugar. Autopsy: Lungs severely congested; liver showed marked fatty degeneration; spleen normal; kidneys slightly pale and anemic; intestines mildly congested; stomach normal.
Cat 19. White. Weight, 1,100 grams.
October 20: 13 cc of 2 per cent caffein (0.236 gram per kilo). About 15 minutes later cat became irritable, reflexes increased, persistent crying, stiffness of extremities, diarrhea present; 4.30 p. m., stiffness of muscles, coordination much disturbed, walked with great difficulty; 4.30 p. m., no new symptoms, persistent crying continued.
October 21: Found dead.
Cat 20. White kitten. Weight, 790 grams.
October 20: 11.35 a. m., 10 cc 2 per cent caffein (0.25 gram per kilo) given subcutaneously; 12 noon, convulsions followed by paralysis; 1.30 p. m., still breathing, apparently in comatose condition, lay on its side, dyspnœa, profuse salivation; 4 p. m., convulsions and death.
The results of the experiments of series B show that a dose of even 0.2 caffein per kilo is very toxic for the cat. Symptoms appeared in one animal 40 minutes after the injection of caffein. Some of them were found dead 18 hours after injection, which means that the duration of life was probably a great deal less since there was evidence that they had been dead for some time. Death occurred quite soon after larger doses were injected. Cat No. 3 died 30 minutes after it received caffein. The amounts employed in these experiments can not be considered therefore as the minimum fatal doses. Smaller doses were then tried, as shown in the experiments of the next series.
Series C.
Experiments were performed on five cats which received from 140 to 155 mg per kilo, as follows:
Cat 24. Striped. Weight, 1,300 grams.
October 25: 10 a. m., 50 cc urine, albumin moderate amount—no sugar; 10 cc caffein injected subcutaneously at 12 noon; 12.30, irritable, cried persistently, no appetite; 4 p. m., no convulsions, but persistent crying.
October 27: Cat was still alive.
Cat 17. Weight, 2,620 grams.
October 12: 9.30 a. m., 65 cc urine collected; more than a trace of albumin present, no reduction of Fehling's solution; 3 p. m., 20 cc 2 per cent caffein (150 mg per kilo) injected subcutaneously; 3.15 p. m., irritable and restless.
October 13: 9 a. m., about 15 cc urine collected, reduction of Fehling's solution marked; osazone test also positive.
Cat 23. Black and white. Weight, 1,645 grams.
October 25: 10 a. m., 140 cc urine collected (since October 23), small amount of albumin present, no sugar.
October 27: 9 a. m., no albumin; no sugar in urine; 11.50 a. m., 12.5 cc caffein injected subcutaneously (0.15 gram per kilo); 1 p. m., convulsions and death.
Cat 7. Striped kitten. Weight, 1,285 grams.
October 11: Urine collected, no albumin, no sugar; 9.50 a. m., 10 cc 2 per cent caffein injected subcutaneously in the back; 10.10, violent convulsions lasting about 30 seconds; 10.20, convulsions of shorter duration; 10.30 convulsions; 10.35, convulsions lasting a few seconds; urine passed about 10.20, contained a moderate amount of albumin, but there was no reduction of Fehling's solution; 10.45, profuse salivation and paralysis; died about 10.50.
Cat 39. Yellow. Weight, 2,285 grams.
April 13: 2.40 p. m., 16 cc 2 per cent caffein (0.14 gram per kilo) injected subcutaneously in the back; 3.45 p. m., cat died.
Of the five experiments of this series three died after doses of 140, 150, and 155 mg per kilo. The other two showed symptoms of toxicity, but survived a dose of 150 mg per kilo which indicated that the minimum fatal dose was probably reached. To test this supposition smaller doses were administered, as shown in the following experiments.
Series D.
Ten cats were used for this series of experiments, and the doses administered varied between 103 and 139 mg per kilo. The results shown in the appended table (p.58) indicate that about 120 to 140 mg of caffein per kilo may induce mild symptoms in some cases. The conclusion may be safely drawn therefore that 150 mg per kilo is approximately the minimum fatal dose for the cat when the drug is given subcutaneously. That smaller doses are, however, by no means to be regarded as always safe is shown in the following experiments.
Series E.
Cat 43. Weight, 3,225 grams.[D]
September 14: 10.20 a. m., 20 cc 2 per cent caffein (0.124 gram per kilo) injected into the back; 11 a. m., tetanus and death. Autopsy: Lungs congested; liver congested and showed hemorrhagic spots in capsules and fatty degeneration; kidneys slightly congested; other organs normal.
Cat 48. Black female. Weight, 3,050 grams.
September 14: 18 cc 2 per cent caffein (0.118 gram per kilo) injected subcutaneously in the back; 10.30 a. m., violent convulsions and death. Autopsy: Lungs congested in spots showing numerous petechia; liver congested; spleen congested; other organs normal.
The diminished resistance to caffein of cats Nos. 43 and 48 might be due to the pathologic changes found on autopsy, for evidence is not wanting that the toxicity of drugs might be greatly altered under pathological conditions. Hunt40 has shown that resistance to acetonitril is considerably diminished in chronic alcoholism. This seems to be true also of other drugs under abnormal conditions. Smaller doses of atropin78 are required in lead poisoning than under normal conditions to produce the same results. The following experiment is of interest in this connection, for in this case a much smaller dose than was given in experiments Nos. 43 and 48 produced the typical symptoms of caffein poisoning and proved to be fatal.
Cat 47, black and white male. Weight, 4,220 grams.
September 15: Received subcutaneously 18 cc 2 per cent caffein (0.084 gram per kilo); no symptoms observed for about six hours.
September 16: No symptoms.
September 17: Weight, 4,250 grams; injected 18 cc 2 per cent caffein (0.084 gram per kilo); tetanus and death after two hours. Autopsy: Severe hemorrhagic pneumonia; kidneys pale, other organs normal.
Since two controls survived the same dose in proportion to the body weight of the animal without showing any symptoms, the assumption is justified that the lower resistance to caffein was due to the presence of pneumonia, thus affording additional support to the view that the toxicity of caffein may be increased in disease.
INJECTION INTO THE PERITONEAL CAVITY.
These experiments were carried out on full-grown and on young subjects. As in previous experiments, doses of different sizes were employed. A dose of 0.2 gram per kilo was tried first and then reduced gradually to 0.1 gram per kilo.
Cat 10. Female. Weight, 2,970 grams.
October 9, 1909: 1.30 p. m., 30 cc 2 per cent caffein (0.2 gram per kilo) injected into the peritoneal cavity; urine examined for albumin and sugar, negative; cat found dead at 2.30 p. m. No urine in the bladder.
Cat 16. Black female. Weight, 2,420 grams.
October 9, 1910: Urine examined for albumin and sugar, negative; 2.30 p. m., 22 cc 2 per cent caffein (0.183 gram per kilo) injected into the peritoneal cavity; found dead at 3 p. m.
Cat 99. Well-fed gray female. Weight, 3 kilos.
June 22, 1911: 3.40 p. m., 15 cc 2 per cent caffein injected into peritoneal cavity; salivation and marked irritability within one hour after injection.
June 24: Alive, appetite good.
Cat 98. Well-fed black male. Weight, 4,100 grams.
June 22: 3.45 p. m., 20.5 cc 2 per cent caffein (0.1 gram per kilo) injected into peritoneal cavity; very irritable a few minutes after injection, no other symptoms.
June 24: No symptoms, appetite good.
Cat 93. Black and white. Weight, 1,450 grams.
June 22: 3 p. m., 30 cc 2 per cent caffein (0.137 gram per kilo) injected into peritoneal cavity; salivation, no other symptoms; under observation until 6 p. m.
June 23: 9 a. m., no urine, cat showed no symptoms.
June 24: 9 a. m., no symptoms, took nourishment as usual.
Cat 87. Well-fed white female. Weight, 2,615 grams.
June 23: 2.45 p. m., 19 cc 2 per cent caffein (0.145 gram per kilo) injected into peritoneal cavity; became irritable and restless.
June 24: 9 a. m., no symptoms, took nourishment as usual.
Cat 97. Gray. Age, 3 months. Weight, 500 grams. Diet, meat.
June 24: 2.25 p. m., 5 cc 2 per cent caffein (0.2 gram per kilo) injected into peritoneal cavity; 4 p. m., no symptoms.
June 29: Died.
Cat 96. Gray and white. Age, 3 months. Weight, 575 grams. Diet, meat.
June 24: 2.20 p. m., 4 cc 2 per cent caffein (0.139 gram per kilo) injected into peritoneal cavity; 3.55 p. m., no symptoms.
June 30: Died.
Cat 95. Black. Age, about 3 months. Weight, 860 grams. Diet, meat.
June 24: 10.15 a. m., 8.6 cc 2 per cent caffein injected into peritoneal cavity, salivation immediately after injection; 10.25, convulsions and paralysis; died 10.45 a. m. Autopsy: Macroscopical examination of the organs, negative.
Cat 94. Black and white. Weight, 790 grams. Age, about 3 months. Diet, meat.
June 24: 10 a. m., 8 cc 2 per cent caffein injected into peritoneal cavity; 4 p. m. under continual observation since injection, cat very irritable, respiration more rapid than normal, diarrhea present.
Examination of the above protocols show that a dose of 2 decigrams per kilo was fatal within one hour to one cat and that a somewhat smaller dose killed another individual in 30 minutes. Amounts under 0.15 gram per kilo were just sufficient to induce mild symptoms, such as increased irritability and salivation, which disappeared within a few hours. In no case were the effects noticeable on the following day. The experiments on young kittens are especially interesting, as they proved, contrary to expectation, to be distinctly more resistant than full grown individuals. The death of Nos. 97 and 96 within five and six days, respectively, can not be ascribed to caffein, since some of the controls also died. Moreover, it will be remarked in this connection that no symptoms appeared in three of the four young kittens after the administration of a dose which was rapidly fatal to adult cats. The rapid death of No. 95 after the same dose forms an exception which can not be accounted for, as macroscopical examination at autopsy proved negative.
ADMINISTRATION BY MOUTH.
Two decigrams per kilo were given at first, but it was found that this amount was surely fatal. The dose was therefore reduced to 0.125 gram per kilo. In all of these experiments caffein was given by means of a soft rubber catheter slipped over the stem of a funnel which served as a stomach tube. A 2 per cent aqueous solution was used throughout these tests except in one case in which caffein was given mixed with the food.
Cat 92. Black and white female. Weight, 1,750 grams.
June 10: 12.05 p. m., 14 cc 2 per cent caffein (0.16 gram per kilo) given by mouth; cat was quiet when tied on holder, struggled only a little when tube was put into stomach; 12.30 p. m., cat vomited, no other symptoms.
June 13: Condition good, appetite good.
Cat 87. White female. Weight, 2,620 grams. Diet, meat.
June 5: 2.15 p. m., 20 cc 2 per cent caffein (0.15 gram per kilo) solution administered by mouth through stomach tube; 2.30 p. m., cat irritable, but no other symptoms; 5 p. m., condition about the same, except that it was more irritable and showed some stiffness of the extremities.
June 13: Alive and in good condition, appetite good, not irritable.
Cat 91. White female. Weight, 3,050 grams.
June 10: 12 noon, 23 cc (0.15 gram per kilo) of 2 per cent caffein administered by mouth, cat struggled violently; 1.30, salivation; 1.40 p. m., convulsions; died at 2 p. m. Autopsy: Congestion of lungs, liver, and spleen; heart vessels injected; other organs normal.
Cat 88. Black and white female. Weight, 3,260 grams. Diet, meat.
June 5: 2.20 p. m., 25 cc of 2 per cent caffein (0.15 gram per kilo) given by mouth; 2.45 p. m., cat irritable, no other symptoms (cat did not vomit after the administration of caffein); 4 p. m., cat found dead. Autopsy: Liver very much congested; heart contracted; body was still warm at the time of autopsy.
Cat 90. White and yellow female. Weight, 2,685 grams. Diet, meat.
June 5: 3.15 p. m., 27 cc of 2 per cent caffein (0.2 gram per kilo) given by mouth through stomach tube, about half an hour later cat became irritable and began to salivate; at 4.30 p. m. salivation became more marked, dyspnœa was well developed, and the cat was quite restless and had tremors; 5 p. m., short spasms of posterior extremities, but lay quietly in the cage most of the time; 5.20 p. m., convulsions of short duration and death, muscular relaxation followed immediately after convulsions, no vomiting, diarrhea observed after administration of caffein, and cat passed about 10 cc of urine.
June 6: 9 a. m., found dead.
Cat 89. White and black female. Weight, 2,860 grams. Diet, meat.
June 5: 3.15 p. m., 28.6 cc (0.2 gram per kilo) of 2 per cent caffein given by mouth through stomach tube, no vomiting observed, nor any other symptoms; 3.30, found dead. Autopsy: Organs normal; liver congested.
Cat 82. Gray female. March 3, weight 2,450 grams; June 6, weight 2,750 grams. Diet, 150 grams of meat daily.
June 7: Given 0.4125 gram of caffein in 150 grams of meat, did not eat.
June 8: Given 0.4125 gram of caffein in 150 grams of meat, refused to eat.
June 9: Given 150 grams of meat without caffein, ate all of it.
June 10: No food given.
June 11: No food given.
June 12: Given 0.4125 gram caffein in 150 grams of meat (150 mg per kilo), ate all of it.
June 13: Found dead. Autopsy: Lungs congested, liver congested; other organs apparently normal.
Cat 100. Gray female. Weight, 2,740 grams. Diet, meat.
July 17: 3 p. m., 17 cc of 2 per cent caffein (124 mg per kilo) given by mouth through stomach tube at 3.20 p. m.; 5 p. m., very irritable, but no other symptoms.
July 18: Under observation all day, no symptoms.
Cat 93. Black and white female. Weight, 1,640 grams.
July 17: 3.30 p. m., 10 cc (0.125 gram per kilo) of 2 per cent caffein given by mouth through stomach tube.
July 18: Under observation all day, no symptoms.
From the results of the experiments of this series it appears that 0.15 gram caffein per kilo may be fatal within a few hours after its administration, even if the drug is mixed with a moderate amount of meat. Experiments 87 and 92 show, however, that this amount may be borne by some individuals without any serious consequences, as the cats were under observation for some time after they received caffein, and no untoward symptoms were noticed in either of them during this time. It may be remarked that cat No. 92 vomited shortly after it received caffein. It is practically certain, therefore, that this amount of caffein in proportion to the weight of the animal will in the great majority of cases prove fatal, and perhaps in a smaller percentage of individuals it is surely toxic if it does not escape absorption. Smaller doses may cause irritability in some individuals, but symptoms referable to nervous symptoms of muscles were absent, as in experiments Nos. 93 and 100. The minimum fatal dose of caffein for the cat when given by mouth is, therefore, 0.15 gram per kilo.
Table 9.—Subcutaneous injection; cats.
SERIES A.
Number. Weight.Caffein per kiloSymptoms.Duration of life.
Grams. Gram.
4 1,440 0.30 65 minutesOver 29 hours.
5 1,396 .30 About 2 hours.
SERIES B.
3 2,854 0.25 30 minutes.
6 1,645 .243 Few minutes 1 hour 30 minutes.
8 1,735 .25 30 minutes. 1 hour.
9 1,960 .25 1 hour 1 hour 45 minutes.
12 1,185 .20 3 hours Less than 18 hours.
14 1,855 .20 1 hour 20 minutes Do.
15 2,145 .20 40 minutes. Do.
19 1,100 .236 15 minutes Do.
20 790 .25 4 hours 30 minutes.
SERIES C.
24 1,300 0.153 1 hour Survived.
17 2,620 .15 15 minutes Do.
23 1,645 .15 1 hour 10 minutes.
7 1,285 .155 20 minutes 1 hour.
9 2,285 .14 65 minutes.
SERIES D.
13 730 0.139 Restlessness
21 1,165 .138 None
25 965 .103 do.
26 1,605 .125 do.
27 1,625 .125 do.
28 2,335 .128 do. Received 2 doses: survived.
40 2,710 .129 do. Do.
41 1,785 .123 do. Do.
42 2,315 .112 do. Do.
38 2,325 .120 Mild Died after second dose.
SERIES E.
43 3,225 0.124 40 minutes.
48 3,050 .118 Died soon after.
47 4,220 .084 Survived.
247 4,250 .084 2 hours.
1 Pathological conditions. 2 Two days after first injection.
Table 10.—Injections into peritoneal cavity; cats.
SERIES A.
Number. Weight.Caffein per kiloSymptoms.Duration of life.
Grams. Gram.
99 3,000 0.100 Mild Survived.
98 4,100 .100 do.1 Do.
93 1,450 .137 Very mild Do.
87 2,615 .145 do. Do.
97 505 .200 None 5 days.
96 575 .139 do. 6 days.
95 860 .200 15 minutes 30 minutes.
94 790 .200 Diarrhea Survived.
10 2,970 .200 1 hour.
16 2,420 .183 30 minutes.
1 In few minutes.
Table 11.—Administration of caffein by mouth; cats.
SERIES A.
Number. Weight.Caffein per kiloSymptoms.Duration of life.
Grams. Gram.
91 3,050 0.15 1 hour 40 minutes 2 hours.
88 3,260 .15 1 hour 40 minutes.
92 1,750 .16 25 minutes Survived.
87 2,620 .15 3 hours Do.
90 2,685 .20 1 hour 15 minutes Less than 18 hours.
89 2,860 .20 75 minutes.
82 2,450 .15 Less than 24 hours.
100 2,740 .124 1 hour 40 minutes Survived.
93 1,640 .125 Do.
SUMMARY.
The toxicity of caffein in cats is shown to be the same when given by mouth as when injected subcutaneously, the minimum fatal doses in both cases being 0.15 gram per kilo. When introduced by the intraperitoneal route, caffein is, on the contrary, distinctly less toxic. After the administration of 0.137 and 0.145 gram caffein per kilo (Nos. 93 and 87) salivation in one cat (No. 93) and irritability and muscular stiffness in the other were the only effects noticed. These symptoms were no longer observed the next day and the cats appeared to be perfectly normal. Experiments with larger doses indicate that the minimum fatal dose by this method of administration is about 0.2 gram per kilo.
EXPERIMENTS ON DOGS.
The experiments were carried out on well-fed adult dogs and on puppies, kept under observation for some time before the drug was administered. Only those manifesting no signs of abnormality were used for these tests. Caffein was given by mouth mixed with 10 to 20 grams of meat, or subcutaneously in 2 per cent aqueous solution. The young animals received caffein dissolved in milk. The determination of the minimum toxic or fatal doses when the drug was fed presented considerable difficulty, as in many instances the ingestion of the drug was closely followed by vomiting.
ADMINISTRATION BY MOUTH.
Series A.
The effective dose in these experiments showed considerable variation. One dog (No. 38) died after a dose of 0.12 gram caffein per kilo, while some subjects survived doses of 0.2 and 0.23 gram per kilo. In the 12 experiments given in Table 12, page 62, it will be noticed that from 0.12 to 0.152 gram per kilo proved fatal to three dogs, while three others survived the same amounts in proportion to the body weight. The results were the same with larger doses. It may be observed in this connection that in the case of the five dogs in which vomiting was noticed some time during the 24 hours following the administration of caffein, four survived, No. 38 being the exception. The greater toxicity of caffein in this case is in all probability due to some morbid process, the presence of which was indicated by the high temperature of this subject.
That vomiting may avert a fatal issue after larger doses of caffein is made further probable by experiment on dog No. 48, for which, in the absence of vomiting, a dose of 0.2 gram of caffein per kilo proved fatal. On this supposition the discrepancy in the results obtained in this series may be readily explained. The smallest doses which proved fatal in these experiments were 0.145 and 0.152 gram per kilo. No. 38, which died from a dose of 0.12 gram per kilo, may be considered as an exception, as this subject was not normal. Experiments with caffein on dogs were made at various other times in this laboratory but failed to show that smaller doses of caffein, even when vomiting did not occur after its administration, were fatal, although toxic effects were observed. The conclusion is therefore justified that the minimum fatal dose of caffein for the normal dog is about 0.15 gram per kilo when given by mouth.
SUBCUTANEOUS INJECTION.
Series B.
To determine the toxicity of caffein more accurately, especially for comparison with animals of other species, the subcutaneous method of administration was also used. The injections were made with a syringe of 20 cc capacity, the contents of which were introduced into contiguous areas. The results of experiments on six dogs indicate that approximately 150 to 160 mg per kilo is the minimum fatal dose, since such doses proved fatal to two out of the three animals receiving this amount, while three others which received doses of from 143 to 160 mg per kilo survived.
EXPERIMENTS ON PUPPIES.
Series C.
In these experiments the resistance of young growing puppies to caffein was studied. Caffein was given by mouth to all the subjects except one, to which it was administered subcutaneously. The protocols, only a few of which are given, and the tabulated data of the experiments (p. 62) show that the age of the animal has a decided influence on the toxicity of caffein.
Dog 11. Weight, 1,260 grams.
August 2: At 10 a. m. given 12.5 cc of 2 per cent of caffein through stomach tube; 2 p. m., had convulsions, diarrhea, salivation, and stiffness of limbs.
August 3: Found dead 9 a. m. Autopsy: Thoracic viscera apparently normal; stomach immensely distended and filled with a white, cheesy mass and some fluid; round worms plentiful in stomach and small intestine; mucosa of entire intestine congested; contents of lower intestine congested; liver pale; spleen flabby; kidney congested.
Dog 10. Weight, 1,650 grams.
July 26: 9.30 a. m., 29 cc of 2 per cent caffein added to 60 cc of milk offered, but refused, and was therefore fed by mouth through stomach tube; 10.25 a. m., no symptoms; 11.30 a. m., restlessness, extremities stiff, post. extremities spread apart, dog shows well-marked symptoms of caffein poisoning; 12.10 p. m., symptoms more severe, extremities extended and spread out, is lying flat on belly so that nose touches floor of the cage; 12.40 p. m., found dead; was alive at 12.10 p. m. Autopsy: Lungs showed hemorrhagic foci in all lobes; heart apparently normal; liver fatty; stomach and intestines filled with round worms; spleen and kidney apparently normal.
Dog 9. Weight, 3,000 grams.
July 25: 350 mg caffein per kilo; 5 p. m., lying down most of the time, occasionally walks about in stall; restlessness present, but not marked; 5.30 p. m., vomit which looked frothy and mucilaginous noticed on the floor of the stall; no meat particles noticed in vomit, though searched for; whines occasionally.
July 26: 9 a. m., looks well; no signs of the effect of caffein given the day previous.
Dog 8. Yellow female. Weight, 3,100 grams.
July 22: 10.50 a. m., received 1.1 grams of caffein in 10 grams of meat (354 mg caffein per kilo); 3 p. m., vomited mucus; gait clumsy; refused to eat; continually drinking water; very restless; 4 p. m., convulsions set in at 3.55 p. m.; tonic rigidity of the posterior extremities; profuse salivation; convulsions were both tonic and clonic in character, and resembled those seen in rabbits in caffein intoxication; a striking feature was the duration of the spasm, which began at 3.55 p. m. and kept up for more than two hours.
July 23: Found dead at 9 a. m.
The data recorded in the table and in the protocols of the experiments of series C show that four out of the seven animals experimented upon died in less than 24 hours after caffein was fed; three of these received 300 to 354 mg caffein per kilo, and one received 200 mg caffein per kilo. No. 8 vomited four hours after caffein was given. No vomiting was observed in the other three dogs. From 0.300 to 0.350 gram of caffein per kilo may be regarded, therefore, as surely fatal to young growing puppies. That this is in all probability the minimum lethal dose appears from the following experiments: No. 9, which received 350 mg per kilo, vomited one hour after and survived, which indicates that some of it was probably not absorbed. The amount which entered the circulation was therefore less than 350 mg per kilo. Since No. 15, which received 250 mg caffein subcutaneously, likewise survived, the probabilities are that 300 to 350 mg per kilo were the minimum fatal doses for these animals. Moreover, No. 12, which received 200 mg caffein per kilo, survived, no vomiting having been observed. The case of No. 11, in which the same amount of caffein in proportion to body weight proved fatal, may be explained perhaps by the findings of the autopsy.
The results obtained in these experiments justify the conclusion that young growing dogs can stand larger doses of caffein than full-grown and older dogs.
Attention may also be called here to the difference in the symptoms produced by caffein in very young and in adult dogs. It was often noticed in these experiments that the symptoms in older subjects when given toxic doses of caffein set in rather abruptly and ended in instantaneous death. We failed to observe this phenomenon after the administration of large amounts of caffein to very young dogs, in which tonic and clonic convulsions alternating with paresis were observed. These symptoms set in rather gradually and lasted several hours (see experiment No. 8), resembling the rabbit in this regard.
SUMMARY.
The toxicity of caffein for adult dogs is about the same, whether given by mouth or injected subcutaneously. The resistance of puppies to caffein is much greater than that of adults.
Table 12.—Administration by mouth; dogs. (Series A.)
No. Weight.Caffein per kiloResults.Remarks.
Kilos. Gram.
47 13.60 0.144SurvivedVomiting observed.
55 12.75 .200 do.Stiffness of muscles; no other symptoms.
56 7.95 .200Found dead next day
52 13.60 .147Survived
57 6.50 .230 do.Vomited after 1 hour; convulsions after 1 hour and 45minutes.
39 23.10 .120 do.Increased frequency of respiration, thirst, loss of appetite, vomited rest of day when he drank water, salivation, restlessness, passed feces frequently.
48 11.50 .174 do.Vomiting observed.
48 12.00 .200Found dead next dayNo vomiting observed. Second dose was given 8 days after first.
54 13.40 .200SurvivedVomiting observed.
49 13.15 .152Found dead next day
38 14.50 .120 do.Symptoms after 1½ hours: Dog had a temperature of 104° F. before caffein was given; vomited 3 hours after caffein was fed.
18 10.80 .145 do.
Table 13.—Subcutaneous injection; dogs. (Series B.)
No. Weight.Caffein per kiloResults.Remarks.
Kilos. Gram.
62 9.30 0.161SurvivedRestlessness and vomiting one-half hour after injection.
61A 14.00 .160Found dead next day
63 12.00 .150SurvivedRestlessness 1 hour after injection.
64 14.00 .150 do.Restlessness and thirst 45 minutes after injection.
59 7.20 .160Died 1 hour and 20 minutes after injection.Marked restlessness, but no convulsion.
61 14.60 .143SurvivedSymptoms observed in 1½ hours.
Table 14.—Administration by mouth to puppies. (Series C.)
No. Weight.Caffein per kilo.Results.Remarks.
Kilos. Gram.
8 3.10 0.354Found dead next dayVomited in 4 hours after feeding; restlessness, loss of appetite, thirst, incoordination of muscles, convulsions.
9 3.15 .350SurvivedMuscular incoordination and stiffness, restlessness, vomited 1 hour after caffein was given.
10 1.60 .350Died in 3 hoursConvulsion; no vomiting.
11 1.26 .200Found deadSalivation; convulsions.
12 1.28 .200SurvivedNo symptoms.
15 1.20 .250 do.Subcutaneous injection.
16 3.50 .300Died in 1 hourConvulsions 45 minutes after caffein was fed.