Caffeine facilitates muscular labor by increasing the activity not of the mus cle itself, but of the corresponding eere bro-spinal centre. As a consequence of this double action on the cerebrum and medulla, the sensation of effort is dimin ished and keeps off fatigue. The drug further prevents loss of breath and pal pitation due to severe muscular effort. It does not check tissue-waste. Caffeine allows more exertion through a kind of physiological economy. The drug would seem to place a person untrained in the position of one who had been subjected to perfect physical training. The inges tion of food allows of a certain amount of exertion, but fatigue conies on before the assimilated products of digestion are used up, and thus a reserve is left. Caffeine seems to use up more or less of that reserve, and hence the drug is beneficial only temporarily. Germain Si!e and Lapicque (Bull. de l'Acad. de M6d., Mar., '90).
Caffeine is thought by some observers to be one of the drugs instinctively de sired by man, because of its exciting in fluences. Caffeine in small, repeated doses, according to this view, may be ad vantageously prescribed to soldiers on the march, as it increases muscular ac tion ancl promotes the activity of the motor-nervous system, both cerebral and medullary. The result of this double action is to diminish the sensation of effort and to prevent fatigue. It pre vents shortness of breath, with resultant palpitation. In this manner it supplies vigor to one who is engaged in severe and prolonged exercise.
Caffeine and theobromine act as direct excitants of the renal parenchyma. In contrast with the saline diuretics, which appear chiefly to provoke elimination of water and at the same time of salts, and especially chlorides, the xanthin bodies increase the elimination of nitrogenous elements, and specially urea and uric acid. Anton (Arch. Inter. de Pharrn, et de Therap., vol. fase. v and vi, 1901).
Poisoning by Caffeine.—James Fergu son observed a case of tonic spasm follow ing- a medicinal dose of citrate of caffeine, repeated three hours later for severe headache, which became more violent than before. There was jerking of the hands and forearms, the fingers began to be rigidly clenched, and shortly after the head was seen to be drawn to one side, with the jaws tightly fixed together. At this stage the author found the fingers of both hands as described, and the mus cles of the face tightly drawn, but with some imperfect articulation by this time possible. Friction of the affected parts did some good, and a dose of 30 grains of chloral was ultimately followed by recovery of control over the muscles. There had been no loss of consciousness throughout. The patient's sensation had been chiefly one of great faintness and nausea. The author suggests that the use of the drug be watched, since it has now become a popular remedy for head ache.
Therapeutics.—European observers— iinchard, Ferrara, and others—state that caffeine, given by the mouth, does not, even in large doses, show its best effects, because it is eliminated with great ra pidity. The hypodermic method is the best, and is painless, producing no cuta neous reaction.
In diseases of the heart—both those depending on degenerative processes in the muscular fibres and such as are termed.functional—the action of caffeine is striking and beneficial. In these affec tions the use of digitalis is only indicated during a later stage of tbe disease, when the heart is no longer capable of fulfill ing its duties, when (-edema and dyspncea have set in. Caffeine is further of great use in attacks of dyspncea, such as are observed in cases of sclerosis of the cor onary arteries, and also in cases of car diac insufficiency following on overexer tion, severe moral shock, or febrile mala d i es.
DROPSY.—In dropsical effusions re sulting not only from heart affections, but from disorders of other viscera, the diuretic properties of caffeine frequently manifest themselves advantageously.
Case of chronic peritonitis in which, under pure caffeine, there was always ob served a markedly-increased diuresis, but with caffeine-sodium salicylate the op posite effect was seen, the caffeine diu resis being suppressed by the salicylate. Caffeine produced its most marked effect after a course of small doses of salicy lates. The use of caffeine alone made tapping of the aseites unnecessary, owing, to the absorption of all the cedema, which, on the other hand, was increased by the use of salicylates. Caffeine rec ommended with or without digitalis in all cases of venous engorgement with intact kidneys in order to remove the cedema by diuresis. Siegert Manch. med. Woch., May 25, '97).
In cardiac dropsy digitalis is tbe most useful drug, but when it does not afford relief caffeine may bc of valuable serv ice. Case in which tbe heart was greatly enlarged, and tbe impulse strongly marked, the apex-beat being in the sev enth space in the anterior axillary line. There were signs also of dilatation of the aorta. -At the apex was a loucl and long, systolic murmur. The caffeine was used according to the following formula:— Caffeince, 5 grains. Sodii salicyl., 4 grains. Aq., ad 1 ounce.-111.
Given twice daily, this mixture af forded considerable relief. Tickell (Clin ical Journal, Feb. 2, '98).
In cardiac and renal disorders the effect of caffeine is usually as follows: With doses of 3 to 4 '/ grains two or three times a day, the blood-pressure rises steadily, slowly, and the quantity of urine is increased. (Edema is lessened, but very slightly. Between the fourth and the sixth day the patients begin to complain of a sense of constriction in the chest, dyspmEa, and restless nights. In some cases it can be made out by aus cultatory percussion that the heart has diminished in size in all its diameters; this is a sign of impending tetanus of the cardiac muscle, and the cafTeine must be at once omitted. CafTeine continues to be excreted in the urine for at least ten to fifteen days after the last dose is taken. The more the kidneys are dis eased, the slower it is excreted and the greater is the danger. Caffeine acts ex actly like strychnine on the spinal cord, the striated and especially the cardiac muscles. Zenetz (Wiener med. Woch., Dec. 9, '99).