Pilocarpine

Pilocarpine is an alkaloid, a natural substance extracted from the leaves of Pilocarpus jaborandi . Due to its muscarinic-type parasympathomimetic activity (interacting with peripheral acetylcholine receptors), pilocarpine is used mainly in ophthalmology as a stimulant for tear secretion. The term parasympathomimetic refers to its ability to stimulate the activities of the parasympathetic nervous system, which promotes rest, relaxation, rest, digestion and energy storage; not surprisingly, pilocarpine is also used to promote salivary secretions, while its ability to increase intestinal peristalsis is known.

Although pilocarpine can promote hair growth, it causes a marked rubefacient effect (if applied locally it induces hyperemia and sweating), and slows down the heartbeat, its main pharmacological applications concern the eye sector. In addition to increasing tearing, in fact, pilocarpine produces a miosis, ie a narrowing of the pupil; in the form of eye drops, it has long been the main drug in the fight against glaucoma, although it can be associated with local disorders, such as watery eyes, conjunctival hypermemia and variations in refractions. In ophthalmology, pilocarpine is also used to reduce the possibility of nocturnal glare in patients who have recently undergone phakic intraocular lens implantation; the use of pilocarpine at low concentrations (1%) would alleviate these symptoms by narrowing the pupil.

As mentioned, in the form of oral tablets, pilocarpine is used in the treatment of xerostomia (dry mouth due to poor salivation), an unpleasant side effect of radiant neck or head therapies. If on the one hand it induces an improvement in salivation, on the other hand this substance promotes increased sweating, pancreatic, intestinal and mucous secretions of the respiratory system; it also increases the tone and motility of smooth muscles in the intestine, urinary tract, bladder, bile ducts and bronchi.

Administered orally, pilocarpine begins to produce the first effects over a period of 20-30 minutes, with a peak after 1 hour and a duration of action of about 3 hours. The absorption rate is reduced if the drug is taken with a high-fat meal. Having an action of short duration, it is necessary to make use of the administration at least twice a day.

The side effects of pilocarpine are those typical of cholinergic stimulation and are dose-dependent; among those that occur most frequently are increased sweating, high frequency, bronchoconstriction, nausea, abdominal cramps, diarrhea, flushing, chills, dizziness and fatigue. Sweating, in particular, is the main cause of treatment suspension. Not by chance, pilocarpine is also used in the so-called sweat test, a useful exam in the diagnosis of cystic fibrosis. In the patients examined, after stimulation with pilocarpine, the concentration of chlorine and sodium in the excreted sweat is measured; in fact, subjects with cystic fibrosis or mucoviscidosis (hereditary disease) have particularly high concentrations of chlorine in sweat.