Pilocarpine

Pilocarpine is a muscarinic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It acts as a muscarinic receptor agonist in the parasympathetic nervous system.

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. This 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 reduced the possibilty of glare at night from lights if the patient underwent implantation of phakic intra-ocular lenses, therefore the use of Pilocarpine would reduced the size of the pupils relieving these symptoms. The most common concentration for this use is Pilocarpine 1%, the weakest concentartion.

Pilocarpine is also used to treat dry mouth (xerostomia). Pilocarpine stimulates the secretion of large amounts of saliva and sweat. It may also cause hypotension and bradycardia in the cardiovascular system, and bronchospasm and increased bronchial secretion in the lungs due to its non-selective muscarinic action.

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).

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 (Pharmacia & Upjohn), 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 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.