The resistance of the guinea pig to caffein, as of the rabbit, is greatest when given by mouth. The minimum fatal dose is less by intraperitoneal injections, but greater than by subcutaneous injections, thus differing from the rabbit in this regard. The adult cat is less resistant than the guinea pig or rabbit to caffein. The minimum lethal dose by mouth is the same as by subcutaneous, and is less than by intraperitoneal, injection. The minimum fatal dose for dogs was found to be the same by mouth as by subcutaneous injection and is almost the same as for the cat. The toxicity of caffein varies in the guinea pig according to season of the year.
Age is likewise a factor in the toxicity of caffein, young animals being more resistant than the full-grown and older animals; this was shown in experiments on rabbits, cats, and dogs. The symptoms of caffein poisoning also were different in puppies and in full-grown dogs. Different diets, such as carrots and oats, did not influence the resistance of rabbits and guinea pigs to caffein. Low protein diet tends to decrease resistance to caffein in dogs. Young growing dogs are less resistant to caffein on a meat than on a milk diet. Caffein is not cumulative in the rabbit or dog, even if administered for a considerable length of time. Some degree of tolerance may be induced in the rabbit under certain conditions, but not in dogs under the conditions of the experiments made in this investigation. The possibility, however, that dogs may acquire tolerance for caffein is not excluded. Although the rabbit tolerates a much larger single dose of caffein than the dog, it was found, in experiments on chronic intoxication that the rabbit is less resistant to caffein than the dog. The toxicity of caffein is probably increased under pathological conditions, since comparatively smaller doses were fatal to rabbits, cats, and dogs, when marked lesions not due to caffein were found at autopsy. Glycosuria was observed in rabbits, guinea pigs, and cats when caffein was given in sufficient amounts.
Table 18.—Acute caffein intoxication: Table showing average minimum toxic and minimum fatal doses for adult animals.
Table headings:
SC: Subcutaneously.
BM: By mouth.
IP: Intraperitoneally.
IM: Intramuscular.
IV: Intravenous.
| Animal. | Effect of dose. | Dose per kilo (grams) | ||||
|---|---|---|---|---|---|---|
| SC. | BM. | IP. | IM. | IV. | ||
| Rabbit, gray | {Toxic | 0.15 | 0.325 | 0.100-0.125 | 0.13-0.15 | 0.05 |
| {Fatal | .30 | .350 | .150 | .20 | 0.10- .16 | |
| Rabbit, white or black | {Toxic | |||||
| {Fatal | .20 | .290 | ||||
| Guinea pig | {Toxic | 0.15- .16 | .150 | .200 | ||
| {Fatal | .20- .24 | 0.280- .300 | .240- .250 | |||
| Cat | {Toxic | .12- .14 | .125 | .125- .150 | ||
| {Fatal | .15 | .150 | .180- .200 | |||
| Dog | {Toxic | .100- .120 | ||||
| {Fatal | .15- .16 | .140- .150 | ||||
Note.—The doses given in this table are approximate.
CAFFEIN BIBLIOGRAPHY.
1. Abderhalden and Brahm. Zts. Physiol. Chem., 1909, 62: 133.