Part 10

+--------+---------+-----------------------+------------------- Number.|Weight. | Caffein | Symptoms. | Duration of life. | |per kilo.| | -------+--------+---------+-----------------------+------------------- |_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._

+--------+---------+-----------------------+------------------- Number.|Weight. | Caffein | Symptoms. | Duration of life. | |per kilo.| | -------+--------+---------+-----------------------+------------------- |_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._)

----+--------+-------+-----------+------------------------------------ | |Caffein| | No.| Weight.| per | Results. | Remarks. | | kilo. | | ----+--------+-------+-----------+------------------------------------ |_Kilos._|_Gram._| | 47 | 13.60 | 0.144 |Survived |Vomiting observed. 55 | 12.75 | .200 | do. |Stiffness of muscles; no other | | | | symptoms. 56 | 7.95 | .200 |Found dead | | | | next day | 52 | 13.60 | .147 |Survived | 57 | 6.50 | .230 | do. |Vomited after 1 hour; convulsions | | | | after 1 hour and 45 minutes. 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 | .200 |Found dead |No vomiting observed. Second dose | | | next day | was given 8 days after first. 54 | 13.40 | .200 |Survived |Vomiting observed. 49 | 13.15 | .152 |Found 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._)

----+--------+-------+-----------+------------------------------------ | |Caffein| | No.| Weight.| per | Results. | Remarks. | | kilo. | | ----+--------+-------+-----------+------------------------------------ |_Kilos._|_Gram._| | 62 | 9.30 | 0.161 |Survived |Restlessness and vomiting one-half | | | | hour after injection. 61A| 14.00 | .160 |Found dead | | | | next day | 63 | 12.00 | .150 |Survived |Restlessness 1 hour after injection. 64 | 14.00 | .150 | do. |Restlessness and thirst 45 minutes | | | | after injection. 59 | 7.20 | .160 |Died 1 hour|Marked restlessness, but no | | | and 20 | convulsion. | | | minutes | | | | after | | | | injection.! 61 | 14.60 | .143 |Survived |Symptoms observed in 1½ hours. ----+--------+-------+-----------+------------------------------------

TABLE 14.--_Administration by mouth to puppies._ (_Series C._)

----+--------+-------+-----------+------------------------------------ | |Caffein| | No.| Weight.| per | Results. | Remarks. | | kilo. | | ----+--------+-------+-----------+------------------------------------ |_Kilos._|_Gram._| | 8 | 3.10 | 0.354 |Found dead |Vomited in 4 hours after feeding; | | | next day | restlessness, loss of appetite, | | | | thirst, incoordination of muscles, | | | | convulsions. 9 | 3.15 | .350 |Survived |Muscular incoordination and | | | | stiffness, restlessness, vomited 1 | | | | hour after caffein was given. 10 | 1.60 | .350 |Died in |Convulsion; no vomiting. | | | 3 hours | 11 | 1.26 | .200 |Found dead |Salivation; convulsions. | | | next day | 12 | 1.28 | .200 |Survived |No symptoms. 15 | 1.20 | .250 | do. |Subcutaneous injection. 16 | 3.50 | .300 |Died in |Convulsions 45 minutes after caffein | | | 1 hour | was fed. ----+--------+-------+-----------+------------------------------------

CHRONIC CAFFEIN INTOXICATION.

The object of this study was to ascertain the effect of repeated dosage when caffein was given daily or at longer intervals. The experiments were tried on rabbits and on dogs. As in the experiments on acute intoxication, the animals were under observation for some time in the laboratory before the administration of caffein was begun in order to ascertain the presence or absence of abnormality. The relation of diet to toxicity received some attention, but the question was not studied exhaustively in the present investigation.

EXPERIMENTS ON RABBITS.

Full-grown adult as well as young rabbits were employed. The diet consisted either of carrots or of oats; water was given ad libitum. The rabbits were kept in metal cages in a well-lighted and well-ventilated room. Unnecessary handling or any other procedure tending to fatigue or to cause discomfort to the animals was very carefully avoided, since we had found that such treatment was likely to decrease the resistance of the rabbit to caffein. The caffein was administered by feeding by mouth and through a stomach tube, or by the subcutaneous method. In a good many cases it was given daily, in some at longer intervals.

SERIES A.

The experiments of this series formed a preliminary study for the purpose of testing the effect of moderate doses. One decigram of caffein per kilo was given daily for several days; when administered at longer intervals the dose was increased to 150 to 200 mg per kilo. It was found that the smaller doses did not produce any symptoms; even the weights of the animals were not influenced. Doses of medium size given on two successive days were likewise without any noticeable effect (Nos. 182, 183, 123, 101). When a third dose of this size was given within 48 or 24 hours it proved fatal (Nos. 123, 182, and 183). Exceptionally, however, moderately large doses (for rabbits) may be given for three consecutive days without fatal issue, as in rabbit No. 101. When given at intervals of two to three days, larger doses, as may be seen from the protocols, can be administered without causing acute death (Nos. 173, 181, 201).

The results of the tests of this series point to the absence of any accumulation and to the possible elimination of moderate doses of caffein and its products of decomposition within 24 hours or thereabouts. When the doses are larger the time of its elimination is apparently longer, as shown by the fact that repetitions of the dose the next day may be fatal, but when a longer interval is allowed it may be given without causing death. It will be observed that only one rabbit of this series survived, but it was extremely emaciated. This condition has been observed in a number of cases after caffein had been given for several days. Even when the drug was withdrawn the animals continued to lose weight. This may be explained by the condition of the gastro-intestinal canal as found at autopsy. The presence of inflammation of the mucous membrane of the stomach and intestines, with ulceration of the mucous membrane of the pylorus in one of the rabbits (No. 173) of the series, in all probability caused diminution or loss of appetite, which of itself would tend to cause loss of flesh and strength and finally death. Protocols of the experiments follow.

_Rabbit 173._ _Carrots were fed from October 1 to 18 and oats for the remainder of the experiment._

+---------+--------- Date. | Weight. | Caffein | |per kilo. ---------+---------+--------- | _Grams._| _Gram._ Oct. 9 | 1,980 | 0.141 Oct. 11 | 1,905 | .190 Oct. 13 | 1,930 | .207 Oct. 16 | 2,005 | 0.220 Oct. 18 | 1,845 | Oct. 20 | 1,740 | .230 ---------+---------+--------

October 21: Paralysis of posterior extremities.

October 22: 9 a. m., found dead.

The urine was examined before and after the administration of caffein. No symptoms were observed after the administration of caffein (5 doses in 11 days), nor was albumen or sugar found in the urine after any of the experiments on this rabbit. _Autopsy_: Pyloric mucosa exhibited several ulcers; small intestines showed slight inflammation; liver deeply congested; kidneys showed marked inflammation of cortex; other organs practically normal.

_Rabbit 181._ _Diet, carrots September 29-October 17, then oats._

+---------+---------- Date. | Weight. | Caffein | |per kilo. ---------+---------+---------- | _Grams._| _Gram._ Oct. 4 | 1,425 | 0.105 Oct. 5 | 1,450 | .100 Oct. 6 | 1,270 | .100 Oct. 7 | 1,210 | .100 Oct. 8 | 1,375 | .130 Oct. 9 | 1,305 | .153 Oct. 11 | 1,370 | 0.175 Oct. 13 | 1,385 | .180 Oct. 16 | 1,345 | .200 Oct. 17 | 1,030 | Oct. 18 | 1,230 | Oct. 20 | 1,215 | ---------+---------+----------

Rabbit was markedly emaciated and weak. No albumen or sugar found in the urine as a result of caffein feeding.

_Rabbit 182._ _Diet of carrots from September 29._

Received caffein subcutaneously as follows:

+---------+----------- Date. | Weight. | Caffein | |per kilo. ---------+---------+----------- | _Grams._| _Gram._ Oct. 4 | 1,765 | 0.100 Oct. 5 | 1,880 | .100 Oct. 6 | 1,750 | .100 Oct. 7 | 1,710 | .100 Oct. 8 | 1,685 | .135 Oct. 9 | | .150 Oct. 11 | 1,605 | .174 ---------+---------+----------

October 12: 11 a. m., 23 hours after caffein was given, convulsions with recovery; rabbit died at 1.30 p. m. No sugar was found in the urine at any time after the administration of caffein. Albumen was present only in one specimen.

_Rabbit 183._ _Diet of carrots from September 29._

Received caffein subcutaneously as follows:

+---------+---------- Date. | Weight. | Caffein | |per kilo. ---------+---------+---------- |_Grams._ | _Gram._ Oct. 4 | 1,385 | 0.100 Oct. 5 | 1,460 | .100 Oct. 6 | 1,385 | .100 Oct. 7 | 1,240 | .122 Oct. 8 | 1,310 | 0.153 Oct. 9 | 1,390 | .142 Oct. 11 | 1,390 | .187 ---------+---------+---------

October 12: 9 a. m., found dead. No albumen was found in the urine. Only one sample contained sugar.

_Rabbit 123._ _White, female._ _Diet, oats._

Received caffein subcutaneously as follows:

+---------+--------- Date. | Weight. | Caffein | | per | | kilo. ---------+---------+--------- |_Grams._ |_Grams._ Apr. 14 | 2,350 | 42 Apr. 16 | 2,250 | 90 Apr. 17 | 2,325 | 86 Apr. 20 | 2,126 | 141 Apr. 21 | 1,965 | 152 Apr. 22 | 1,876 | 160 ---------+---------+---------

Rabbit died 30 minutes after last injection of caffein. _Autopsy_: Stomach exhibited marked inflammation of mucosa. Slight enteritis. Liver and kidneys were deeply congested and dark colored.

_Rabbit No. 101, white male._ _Diet, oats._

Received caffein subcutaneously as follows:

+---------+--------- Date. | Weight. | Caffein | | per | | kilo. ---------+---------+--------- |_Grams._ |_Grams._ Mar. 18 | 2,025 | 0.100 Mar. 19 | 1,970 | .100 Mar. 20 | 2,009 | .100 Mar. 22 | 1,855 | .100 Mar. 23 | 1,738 | .114 Mar. 24 | 1,815 | .166 Mar. 25 | 1,830 | .185 Mar. 26 | 1,710 | .176 Mar. 29 | 1,734 | .219 Apr. 1 | 1,606 | .224 ---------+---------+---------

April 5: Found dead. _Autopsy_: Marked inflammation of gastric mucosa. Considerable enteritis affecting the whole extent of the intestines; liver congested and friable; kidneys deeply congested in cortical and medullary portions; spleen congested, but of normal size; lungs and heart normal.

Four days, 0.1 per kilo; 10 doses in 14 days.

_Rabbit 201._ _Diet of carrots begun October 1; October 19, oats._

Subcutaneous injections as follows:

+---------+--------- Date. | Weight. | Caffein | | per | | kilo. ---------+---------+--------- |_Grams._ |_Grams._ Oct. 9 | 1,000 | 0.150 Oct. 11 | 1,015 | .180 Oct. 13 | 1,065 | .187 Oct. 16 | 1,065 | .225 Oct. 18 | 850 | Oct. 20 | 890 | .111 ---------+---------+---------

Under observation six hours October 20; no symptoms.

October 23: Died; was much emaciated but did not show any symptoms; emaciation set in when caffein was withdrawn; urine never contained sugar or albumen; symptoms observed after second dose only.

SERIES B.