A feebly basic substance obtained from the dried leaves of Thea Sinensis, the dried seeds of Coffea Arabica, and from other plants. Official.

Caffeine is a purin derivative, is quickly absorbed, has no important action on the gastro-intestinal tract, and is eliminated by the kidneys, acting powerfully as a diuretic.

The heart-beat is quickened and increased in force; it constricts the blood-vessels at first, but finally dilates them, first dilating the renal vessels. It causes the kidneys to take up an increased quantity of oxygen. The central nervous system is stimulated, causing wakefulness. This action is more marked when taking caffeine, or caffeine-bearing soda drinks, than when in the natural association of the drug in coffee or tea. In toxic or even in excessive doses, the coordination of ideas is disturbed, with more or less intoxication, exaggerated reflexes, spasmodic movements, and even convulsions. Striated muscle is stimulated.

Therapeutics

Useful in poisoning by morphine, chloral, and other narcotics, though inferior to strychnine.

Caffeine (or hot tea or coffee) lessens central depression and may well be given to offset undesirable properties of the antipyretics, especially those of the coal-tar group. It is a diuretic useful in dropsy and to aid in the elimination of toxic substances.

It is useful in the heart failure of pneumonia and septic infections. With phenacetin, it is employed in migraine and periodic headaches.

The dose is 2 grains; of citrated caffeine, 5 grains.

There are several xanthine derivatives, some surpassing caffeine in diuretic effect. Theobromine (5 to 8 grains) is a good diuretic in the edemas and is not so apt to induce insomnia as caffeine. Theo-bromine-Sodium Acetate (8 to 15 grains) is more soluble and better tolerated by the stomach. Agurin is similar to the last-named. Thephorin (7 1/2 grains) is also diuretic. Uropherin-B (5 to 15 grains) is used in connection with digitalis. Theophyllin is a powerful diuretic, but not lasting. It should be followed by other agents (dose 3 to 5 grains). Theophyllin Sodio-Acetate is given in the same dosage. See "New and Nonofficial Remedies" for details. Xanol, caffeine sodio-salicylate from natural oil, is a vaso-motor heart tonic and diuretic (2 to 5 grains).