Pilocarpinae Nitras, B.P., Pilocarpine Nitrate.
Pilocarpine nitrate, C11H16N2O2, HNO3, a salt of the alkaloid pilocarpine, obtained from jaborandi leaves. It is also official in the U.S.P. It may be prepared by neutralising diluted nitric acid with pure pilocarpine and evaporating the neutral aqueous solution thus obtained to dryness on a water-bath. The residue is taken up with boiling alcohol, from which it is allowed to crystallise; 100 parts of the salt contain 76.75 parts of the base. Pilocarpine nitrate occurs in the form of white, distinct crystals, or as a micro-crystalline anhydrous, odourless powder, having a faintly bitter taste; it is permanent in the air. Melting-point not below 173°. A concentrated, aqueous solution gives no precipitate on the addition of solution of ammonia, nor with solutions of sodium or potassium hydroxide (distinction from other alkaloids). If 1 or 2 centigrams of the salt be dissolved in 2 mils of distilled water in a test-tube, 2 mils of a slightly acidified solution of hydrogen peroxide added and a small layer of benzene be carefully poured upon the liquid, then if 3 or 4 drops of a solution of potassium bichromate (1 in 300) be added and the mixture gently shaken, the benzene layer will acquire a violet colour, while the aqueous layer will remain yellow (distinction from other alkaloids). Commercial pilocarpine nitrate is said to contain variable amounts of isopilocarpine nitrate, which lower the melting-point, the chemically pure salt melting at 177° to 178°. Rotation in aqueous solution, not lower than +80°. On ignition it leaves no residue.
Soluble in water (1 in 8), alcohol (1 in 50); almost insoluble in ether or chloroform.
Action and Uses.—Pilocarpine stimulates the terminations of certain nerves supplying unstriped muscle, the heart, and secretory glands. After administration of the drug the secretion of the salivary, sweat, gastric, intestinal, lachrymal, and mucous glands of the mouth, nose, and respiratory tract is augmented. Its action on plain muscle results in increased movements in the alimentary tract, causing perhaps nausea, colic pains, and diarrhoea. The bronchioles are constricted, so that the amount of air entering and leaving the lungs is very much diminished, an "asthmatic" condition resulting. Its action upon the terminations of the third nerve in the eye causes contraction of the pupil, with reduced intra-ocular pressure. Small doses of pilocarpine quicken the heart and raise blood pressure, but large doses have the opposite effect. Pilocarpine nitrate is given by the mouth or hypodermically, principally as a powerful diaphoretic, especially in dropsy due to renal disease and in uraemia, but it is contra-indicated in cardiac dropsy on account of its depressing action. It is sometimes given in bronchitis and in asthma, to stimulate the broncho-dilator fibres when the constrictor fibres are fatigued, and is employed, with potassium bromide, in epilepsy and nervous affections. In ophthalmic surgery, pilocarpine nitrate is employed, like physostigmine, to contract the pupil and reduce intra-ocular pressure in glaucoma, detachment of the retina and intra-ocular haemorrhage. A slight increase of tension at first occurs, and the contraction is less complete, and of shorter duration, than that produced by physostigmine. The action of pilocarpine is in all cases antagonised by atropine. Pilocarpine nitrate is best administered by hypodermic injection in doses of from 1/10 to ¼ grain. Pills may be prepared with milk sugar and glucose. Larger initial doses than 1/20 grain by the mouth are not well tolerated. For ophthalmic use 0.5 per cent. solutions are suitable. Pilocarpine nitrate has been used with good results in aural vertigo and tinnitus aurium; it has been recommended for use in lotions (1 in 250) to promote the growth of the hair, its effect being attributed to stimulation of the glands of the scalp. In cases of poisoning by pilocarpine the stomach should be emptied, and belladonna given by the mouth or atropine hypodermically.
Dose.—3 to 30 milligrams (1/20 to ½ grain).
- Guttae Pilocarpinae, B.P.C.—PILOCARPINE EYE DROPS.
- Pilocarpine nitrate, 0.5 per cent. Pilocarpine contracts the pupil and diminishes intra-ocular pressure.
- Injectio Pilocarpinae Hypodermica, B.P.C.—HYPODERMIC INJECTION OF PILOCARPINE.
- Pilocarpine nitrate, 3 per cent. Five decimils (0.5 milliliters) contain 15 milligrams of pilocarpine nitrate (¼ grain in 8 minims). Dose.—1 to 5 decimils (0.1 to 0.5 milliliters) (2 to 8 minims).
- Lamellae Pilocarpinae, B.P.C.—PILOCARPINE EYE DISCS. 1/400 grain.