|Trade names||Isopto Carpine, Salagen, others|
|topical (eye drops), by mouth|
|Drug class||Miotic (cholinergic)|
|Elimination half-life||0.76 hours (5 mg), 1.35 hours (10 mg)|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||208.257 g/mol g·mol−1|
|3D model (JSmol)|
Pilocarpine is a medication used to reduce pressure inside the eye and treat dry mouth. As eye drops it is used to manage angle closure glaucoma until surgery can be performed, ocular hypertension, primary open angle glaucoma, and to bring about constriction of the pupil following its dilation. However, due to it's side effects it is no longer typically used in the long term management. Onset of effects with the drops is typically within an hour and lasts for up to a day. By mouth it is used for dry mouth as a result of Sjogren's syndrome or radiation therapy.
Common side effects of the eye drops include irritation of the eye, increased tearing, headache, and blurry vision. Other side effects include allergic reactions and retinal detachment. Use is generally not recommended during pregnancy. Pilocarpine is in the miotics family of medication. It works by activating cholinergic receptors of the muscarinic type which cause the trabecular meshwork to open and the aqueous humor to drain from the eye.
Pilocarpine was isolated in 1874 and has been used to treat glaucoma for more than 100 years. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about US$1.61–4.88 per 10 ml bottle. In the United States a month of the drops costs less than $25 as of 2015. It is one of the lowest cost medications for glaucoma. It was originally made from the South American plant Pilocarpus.
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.
Pilocarpine is sometimes used immediately before certain types of corneal grafts and cataract surgery. In ophthalmology, pilocarpine is also used to reduce symptomatic glare at night from lights when the patient has undergone implantation of phakic intraocular lenses; the use of pilocarpine would reduce the size of the pupils, partially relieving these symptoms.[dubious ] The most common concentration for this use is pilocarpine 1%. Pilocarpine is shown to be just as effective as apraclonidine in preventing intraocular pressure spikes after laser trabeculoplasty.
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 salivation, sweating, bronchial mucus secretion, bronchospasm, bradycardia, vasodilation, and diarrhea. Eye drops can result in brow ache and chronic use in miosis.
Mechanism of action
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. Paradoxically, when pilocarpine induces this ciliary muscle contraction (known as an accommodative spasm) it causes the eye's lens to thicken and move forward within the eye. This movement causes the iris (which is located immediately in front of the lens) to also move forward, narrowing the Anterior chamber angle. Narrowing of the anterior chamber angle increases the risk of increased intraocular pressure.
Society and culture
Plants in the genus Pilocarpus are the only known sources of pilocarpine, and commercial production is derived entirely from the leaves of Pilocarpus microphyllus (Maranham Jaborandi). This genus grows only in South America, and Pilocarpus microphyllus is native to several states in northern Brazil.
Pilocarpine is extracted from the powdered leaf material in a multi-step process. First the material is treated with ethanol acidified with hydrochloric acid, and the solvents removed under reduced pressure. The resultant aqueous residue is neutralized with ammonia and put aside until the resin has completely settled. It is then filtered and concentrated by sugar solution to a small volume, made alkaline with ammonia, and finally extracted with chloroform. The solvent is removed under reduced pressure.[verification needed]
The wholesale cost in the developing world is about US$1.61–4.88 per 10 ml bottle. In the United States a month of the drops costs less than $25. It is one of the lowest cost medications for glaucoma.
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).
Pilocarpine is used to induce chronic epilepsy in rodents, commonly rats, as a means to study the disorder's physiology and to examine different treatments. Smaller doses may be used to induce salivation in order to collect samples of saliva, for instance, to obtain information about IgA antibodies.
Pilocarpine is given in moderate doses (about 2 mg) to induce emesis in cats that have ingested foreign plants, foods, or drugs. One feline trial determined it was effective, even though the usual choice of emetic is xylazine.
- Cevimeline—a similar parasympathomimetic medication for dry mouth (xerostomia)
- Bethanechol—a similar muscarinic parasympathomimetic with longer lasting effect
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Pilocarpine is no longer routinely used for long term IOP control due to a poor side effect profile
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