pilocarpine

pilocarpine, naturally occurring alkaloid obtained from plants of the genus Pilocarpus (family Rutaceae). By mimicking the effects of acetylcholine, pilocarpine acts as a stimulant of the parasympathetic nervous system. It promotes the flow of saliva and urine and increases perspiration. Because it increases the outflow of fluid from the eye, reduces the pressure within the eye, and causes the pupil to contract, the drug is used to treat some types of glaucoma. It is also used for some tongue disorders.

Pilocarpine is a muscarinic alkaloid obtained from the leaves of tropical 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.

Clinical uses

Pilocarpine has 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 and produce 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.

In ophthalmology pilocarpine is also used to reduce the possibility of glare at night from lights if the patient underwent implantation of phakic intraocular lenses; the use of pilocarpine would reduce the size of the pupils, relieving these symptoms. The most common concentration for this use is pilocarpine 1%, the weakest concentration.

Pilocarpine is also used to treat dry mouth (xerostomia), e.g. as a side effect of radiation therapy for head and neck cancers. Pilocarpine stimulates the secretion of large amounts of saliva and sweat.

Pilocarpine is used to stimulate sweat glands in a sweat test to measure the concentration of chloride and sodium that is excreted in sweat. It is used to diagnose cystic fibrosis (CF).

Trade names

Pilocarpine is available under several trade names such as: Diocarpine (Dioptic), Isopto Carpine (Alcon), Miocarpine (CIBA Vision), Ocusert Pilo-20 and -40 (Alza), Pilopine HS (Alcon), Salagen (MGI Pharma), Scheinpharm Pilocarpine (Schein Pharmaceutical), and Timpilo (Merck Frosst).

Adverse effects

Use of pilocarpine may result in a range of adverse effects, most of them related to its non-selective action as a muscarinic receptor agonist. Pilocarpine has been known to cause excessive sweating, excessive salivation, bronchospasm, increased bronchial mucus secretion, bradycardia, hypotension, browache (when used as eye drops) and diarrhea. It can also result in miosis when used chronically as an eye drop.

The therapeutic uses of pilocarpine are limited by its adverse effects.