Pilocarpine

Pilocarpine is a drug used to treat dry mouth and glaucoma. It is a parasympathomimetic alkaloid obtained from the leaves of tropical South American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist in the parasympathetic nervous system, which acts therapeutically at the muscarinic acetylcholine receptor M₃ due to its topical application, e.g., in glaucoma and xerostomia.

It is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.

Medical uses

Pilocarpine stimulates the secretion of large amounts of saliva and sweat. It is used to treat dry mouth (xerostomia), particularly in Sjögren's syndrome, but also as a side effect of radiation therapy for head and neck cancer.

It has also been used in the treatment of chronic open-angle glaucoma and acute angle-closure glaucoma for over 100 years. It acts on a subtype of muscarinic receptor (M₃) found on the iris sphincter muscle, causing the muscle to contract -resulting in pupil constriction (miosis). Pilocarpine also acts on the ciliary muscle and causes it to contract. When the ciliary muscle contracts, it opens the trabecular meshwork through increased tension on the scleral spur. This action facilitates the rate that aqueous humor leaves the eye to decrease intraocular pressure.