Pilocarpine

Pilocarpine is an alkaloid, a natural substance extracted from the leaves of Pilocarpus jaborandi. Due to its muscarinic parasympathomimetic activity (it interacts with peripheral acetylcholine receptors), pilocarpine is used above all 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 stillness, 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, causes a marked rubefacient effect (if applied locally it induces hyperemia and sweating), and slows the heartbeat, its main pharmacological applications concern the ophthalmology sector. In addition to increasing lacrimation, pilocarpine produces a miosis, that is, a narrowing of the pupil; in the form of eye drops, it has been for a long time the main drug in the fight against glaucoma, although it can be associated with local disorders, such as lacrimation, 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 tablets to be taken orally, pilocarpine is used in the treatment of xerostomia (dry mouth due to poor salivation), an unpleasant side effect of radiation therapies in the neck or head. If on the one hand it induces an improvement in salivation, on the other this substance promotes an increase in sweating, pancreatic and intestinal secretions and mucous secretions of the respiratory system; it also increases the tone and motility of smooth muscles in the intestine. , urinary tract, bladder, biliary tract and bronchi.

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

The undesirable effects of pilocarpine are those typical of cholinergic stimulation and are dose-dependent; among those that occur with greater frequency we remember increased sweating, pollakiuria, bronchoconstriction, nausea, abdominal cramps, diarrhea, flushing of the face, chills, dizziness and asthenia. Sweating, in particular, is the main cause for discontinuing treatment. Not surprisingly, pilocarpine is also used in the so-called sweat test, a useful test 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.