A Pharmacopoeia is a book compiled by a recognized authority and containing a list of drugs with information concerning them. The United States Pharmacopoeia is not published by the government, as is the case in some countries, but it is accepted by the government as standard in as far as it goes, and this gives it all necessary prestige. For example, the ' Pharmacopoeia fixes the strength of tincture of opium at 10 per cent., and the government requires that for government use, interstate commerce, etc., a preparation to be called tincture of opium must have 10 per cent. strength. State drug laws also recognize the Pharmacopoeia as does the federal government.

The United States Pharmacopoeia was first published in 1820, and each ten years it is revised by a committee selected by the Pharmacopoeial Convention, which is composed of representatives from incorporated medical and pharmaceutical colleges and associations and the Army, Navy and Public Health Service.