Caffeine (C5H(CH3)3N402 .H20 = 210.64) is a feebly basic substance derived from the berries of Coffea Arabica and from the dried leaves of Thea Chinensis.

Pharmacodynamics.

Central Nervous System. - Caffeine stimulates the entire system, but especially the higher psychical functions. This effect is much more marked when a previous depression exists.

Muscular System. - Irritatively stimulated.

Respiration is increased and strengthened; centric action.

Heart rate may be increased for short period from local irritation; then later may be slowed from centric inhibition.

Blood-pressure may be increased slightly by centric vasoconstrictor action.

Alimentary tract may be irritated by habitual use of caffeine.

Secretory Glands. - Caffeine stimulates the secretory epithelium of the kidney, and increases circulation through the renal vessels.

Metabolism is moderately stimulated.

Temperature is elevated by centric action, with big doses only.

Absorption is fairly rapid from gastro-intestinal tract.

Excretion. - Caffeine is eliminated in the urine, chiefly, in the form of urea and some xanthin compounds.

Tolerance may be attained to some degree.

Symptoms.

Moderate Doses.

Heightened mentality, sensory side. Diminished mentality, motor side. Restlessness and insomnia. Augmented physical ability. Heightened sense of touch. Increased pulse rate (by 6 to 8).

Large Doses.

Ringing in the ears. Sense of cerebral pressure. Confusion of thought. Great restlessness. Exaggerated spinal reflexes.

Symptoms arising from chronic Caffeinism:

Nervousness. Cardiac irregularities. Headache and insomnia. Irritability.

Moodiness.

Alternations of optimism and despondency. Lassitude and indisposition.

Therapeutics.

Caffeine may be used advantageously as a respiratory stimulant, to combat depressed conditions of the nervous system, and as a diuretic in dropsical conditions.

Dosage.

Caffeina, 0.03 to 0.15 Gm. Caffeina citrata, 0.06 to 0.3 Gm.

Caffeine 60

Crimson = stimulation. Green = irritation.