C11H16N2O2 = 208.148
Pilocarpine is an alkaloid obtained commercially from jaborandi leaves, in which it occurs in very variable quantity, but rarely more than 0.5 per cent., and is associated with a small proportion of its isomer, isopilocarpine. The pure alkaloid is best obtained by adding excess of ammonia to an aqueous solution of one of its salts, and extracting with chloroform, washing the latter to remove ammonia. On evaporation or distillation of the chloroform, a colourless oily liquid remains, which may be freed from the last traces of solvent by exposing to the air in an open dish for several days. All efforts to crystallise the base have so far failed. Pilocarpine occurs as a colourless thick syrupy liquid, which becomes thinner on warming. With acids it forms salts which crystallise well, the most useful medicinally being the nitrate, on account of its stability in the air. The hydrochloride is hygroscopic. Pilocarpine hydrobromide (C11H16N2O2HBr = 289.076) occurs in white crystals. Soluble in water and in alcohol. Melting-point, 185°. It is used for similar purposes, and given in similar doses, to pilocarpine hydrochloride. By the action of heat or alkalies pilocarpine is readily converted into its isomer, isopilocarpine; the conversion is quantitative by heating with water in a scaled tube at 180° for four hours. The isomer is very similar in its chemical properties to pilocarpine; it is a syrup which can be distilled unchanged in vacuo, and forms crystalline salts with acids. It occurs naturally in small quantity in jaborandi leaves, but the greater portion is formed during the process of manufacture.
Easily soluble in water, alcohol, or chloroform.
Action and Uses.—The properties of pilocarpine are described in the monograph on Pilocarpinae Nitras, its most commonly used salt.