This section is from the book "A Practitioner's Handbook Of Materia Medica And Therapeutics", by Thos. S. Blair. Also available from Amazon: A Practitioner's handbook of Materia Medica and Therapeutics.
Caffeine acts upon the spinal reflex centers, stimulates cerebration, is a direct stimulant to the heart muscle and the respiratory center, and is diuretic. It is employed in nervous headache (I gr. caffeine; every half-hour until relieved, or moderate doses of hydrobromate of caffeine compound), in weak heart action; (preferably 5 to 10 drops hypodermically of the salicylate of caffeine solution *), but when no decided stimulation is desired the citrated caffeine in 2 to 10 gr. doses or moderate amounts of strong coffee. In uremic coma, caffeine should be used hypodermically