§ 496. Pilocarpine (C11H16N2O2) is a soft gelatinous mass, but it forms with the mineral acids crystallisable salts. The solutions are dextra-rotatory. On boiling with water, it decomposes into trimethylamine and m-pyridine lactic acid,
hence it is a pyridine derivative, and its graphic formula probably
The nitrate and hydrochloride are at present much used in pharmacy. Pilocarpine gives a precipitate with phosphomolybdic acid, potassio-mercuric iodide, and most general alkaloidal reagents, but none that are very distinctive. When a solution of gold chloride is added to one of pilocarpine, a salt falls, having the composition C11H16N2O2,HCl + AuCl3. It is not very soluble in water (about 1 in 4600), and has been utilised for the estimation of pilocarpine. Pilocarpine fused with potash yields trimethylamine, carbon dioxide, butyric, and traces of acetic acid. Pilocarpine dissolves without the production of colour in sulphuric acid; but, with bichromate of potash and sulphuric acid, a green colour is produced. It may be extracted from an aqueous solution made alkaline by ammonia, by shaking up with chloroform or benzene.
§ 497. Tests.—When a little of the alkaloid is mixed with ten times its weight of calomel, and rubbed, and moistened by the breath, the calomel is blackened; cocaine also acts similarly; but the two could not be mistaken for each other. If a solution of mercur-potassium iodide is added to a solution of the hydrochloride, the amorphous precipitate becomes, in the course of a day or two, oily drops. “A solution of iodine in potassium iodide gives in pilocarpine solutions a brown precipitate that often crystallises to feathery brown crystals (microscopically), and of serrated form, something like the blade of a scroll-saw, when the crystallisation is incomplete.”—Flückiger’s Reactions.
§ 498. Effects.—Pilocarpine, given subcutaneously in doses of about 32 mgrms. (1⁄2 grain), causes within five minutes a profuse perspiration and salivation, the face becomes flushed, and the whole body sweats; at the same time, the buccal secretion is so much increased that in a few hours over a pint may be secreted. The tears, the bronchial secretion, and the intestinal secretions are also augmented; there are generally headache and a frequent desire to pass water; the pulse is much quickened, and the temperature falls from 1°·4 to 4°: the symptoms last from two to five hours. Langley has shown that the over-action of the submaxillary gland is not affected by section either of the chorda tympani or of the sympathetic supplying the gland. Although pilocarpine quickens the pulse of man, it slows, according to Langley,[542] the heart of the warm-blooded animals, and that of the frog. With regard to the frog, Dr. S. Ringer’s researches are confirmatory. With large doses the heart stops in diastole. If to the heart thus slowed, or even when recently stopped, a minute quantity of atropine be applied, it begins to beat again. There is also a most complete antagonism between atropine and pilocarpine in other respects, atropine stopping the excessive perspiration, and relieving the headache and pain about the pubes, &c. Pilocarpine, given internally, does not alter the size of the pupil, but the sight may, with large doses, be affected. If a solution is applied direct to the eye, then the pupil contracts. No fatal case of its administration has occurred in man. The probable dangerous dose would be about 130 mgrms. (2 grains) administered subcutaneously. Pilocarpine must be classed among the heart poisons.