Cyclopentolate Hydrochloride

Cyclopentolate hydrochloride functions as an antimuscarinic (anticholinergic) agent that blocks cholinergic stimulation at muscarinic receptors located on the sphincter muscle of the iris and the accommodative muscle of the ciliary body. This competitive antagonism prevents the responses typically mediated by acetylcholine, resulting in pupillary dilation (mydriasis) and paralysis of accommodation (cycloplegia). The drug acts rapidly after topical ocular instillation, with maximal cycloplegia achieved within 25 to 75 minutes. Complete recovery of accommodation usually requires 6 to 24 hours, while mydriasis may persist for several days in some individuals, particularly those with heavily pigmented irides. Heavily pigmented irides may require more doses or higher concentrations than lightly pigmented irides to achieve the same effect. This mechanism enables comprehensive ophthalmic examinations, including accurate refractive error assessment and thorough fundus evaluation.

Fig. 1 RRS spectra of Cyclopentolate (CYP), erythrosine dye and its reaction product with CYP. (Abu-Hassan A A. 2025)