This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Phenacetine is slightly soluble in water, but freely soluble in alcohol, and has proven to be a most reliable antineuralgic without deleterious effects. It causes no nausea, vomiting or diarrhoea; no collapse, no cyanosis, or depressing after-effects. It is thought to produce its effects by slowly dissolving in the lactic acid of the stomach.
The mode of action is probably a direct influence on the central nervous system - that of the vaso-motor more especially, for phenacetine acts especially on the vaso-motor neuroses, which indicates a powerful effect on the circulation. Phenacetine is a strong analgesic, and thought to be more powerful in its action than either antipyrine or antifebrin, and it acts very rapidly notwithstanding its insolubility in the gastric juice. About twenty minutes after its administration its effects may be observed. It is employed in the various forms of neuralgia, hemicrania, acute rheumatism, vaso-motor neuroses, neurasthenia, locomotor ataxia, etc., etc.
As an antineuralgic the dose ranges from eight to twenty-two and a half grains (one-half to one and one-half grams). Fifteen grains is the average dose. Good results are obtained by administering phenacetine in gr. v doses, once in an hour until gr. xv-xx are taken.