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.
Salol, Phenylis Salicylas, U. S. P. This synthetic chemical is broken up into phenol and salicylic acid by the action of the pancreatic juice; hence its action is that of these two agents. Its advantage consists in the fact that these valuable antiseptics thus pass the stomach intact and really reach the intestinal tract. About 40% of phenol is liberated, and large doses should be given very guardedly and not at all if the kidneys are inactive. The larger doses used are indicated as an intestinal antiseptic and in rheumatism, and the smaller doses in cystitis, urethritis, etc. The U. S. P. states the average dose as 70 gr., which I consider too high, as it is equivalent to 4 gr. of phenol, the average dose of which is I gr. Personally, 2 to 5 gr. seem a proper dose, especially since they are quite effective. As an antipyretic and analgesic too large doses are required to be within the bounds of assured safety. As high as 90 gr. in twenty-four hours have been recommended, but some gentlemen become overenthusiastic with internal antiseptics. These same men would not think of giving 36 gr. of phenol in enteric pills in twenty-four hours, yet that is what, in effect, they are doing.