Table 11.—Administration of caffein by mouth; cats.
| SERIES A. | ||||
|---|---|---|---|---|
| Number. | Weight. | Caffein per kilo | Symptoms. | 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.