On the other hand, topical administration of pilocarpine has been shown to affect the morphology and survival of meibomian gland epithelial cells. 7 Due to pilocarpine’s effect on salivation, it is also approved orally for the treatment of xerostomia (dry mouth) resulting from radiation exposure. It was also shown to be well-tolerated, with the most common side effects being sweating and increased salivation. One study showed improvement in Schirmer’s testing, ocular surface disease index and tear breakup time. Because of its parasympathetic activity, it can increase lacrimation and has been shown to improve both dry eye symptoms and tear film quality. Studies also indicate that oral administration of a pilocarpine 20mg daily dose can serve as treatment for Sjögren’s-related dry eye. Other risks include patients with pseudoexfoliation syndrome, phacomorphic glaucoma and malignant glaucoma. For example, a patient with spherophakia who has a highly convex lens and weak zonules will have anterior displacement of the iris-lens diaphragm into the anterior chamber. 5 While pilocarpine treatment normally increases the width of the angle due to reduced iris thickness, it can cause acute angle closure in rare cases. 5,6 As such, pilocarpine is a known treatment for glaucoma secondary to acute angle closure from mydriasis or pupil block.Ī necessary consequence of this mechanism of action is pupillary miosis. Its action on the smooth muscle stimulates the iris sphincter and results in the iris pulling away from the trabecular meshwork and aqueous outflow, increasing the eye’s ability to lower IOP. 4 Other ConsiderationsĪlthough it is no longer first-line, pilocarpine has long been used in the management of elevated intraocular pressure (IOP) in glaucoma. It also affects accommodation due to its action on the ciliary muscle. 3 This action substantiates the amount of acetylcholine, resulting in constriction of the pupil by stimulating the sphincter. Because the underlying pathophysiologic mechanism is a result of damage to the postganglionic parasympathetic nerve of the iris sphincter, which is made up of smooth muscle, pilocarpine testing can help elicit the diagnosis.Īdministration of either 0.125% or 0.062% pilocarpine in the affected eye, in dim lighting, can help assess cholinergic supersensitivity. Additionally, there are accommodative paresis and slit lamp findings such as segmental iris palsy. Diagnostically, it can help with the diagnosis of Adie’s tonic pupil, which is characterized by the loss of the direct and indirect pupillary light response. Pilocarpine is not readily used in the clinical setting. 1 Clinical UsesĬontraction of the ciliary muscle enables Vuity’s improvement of near vision acuity in patients responsive to such action. The parasympathetic effects it has on these areas stimulate salivary gland function, increasing salivation and smooth muscle contraction. This receptor is expressed in salivary glands and smooth muscle cells, in addition to other areas throughout the body. Specifically, its action on the M3 receptor is most pertinent to its ocular uses. The expression and actions of each vary, and pilocarpine works primarily on the M1 through M3 subtypes, eliciting parasympathetic effects. There are five different types of muscarinic acetylcholine receptors: M1 through M5. In order to understand its effects, it is important to first be aware of the muscarinic receptors in the body and their mechanisms of action. It can be administered topically or orally. Pilocarpine is a muscarinic acetylcholine agonist. With its newly approved use, it is time to re-explore this topical agent and its many (sometimes overlooked) ophthalmic uses as well as potential adverse side effects to be on the lookout for. 1,2 Although this drug has been around for several decades chiefly as a glaucoma therapy, it has not been routinely prescribed in recent years. A once-commonly used topical ophthalmic medication, pilocarpine has recently re-emerged and gained popularity as a novel treatment for presbyopia.
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