Clinical comparison of pilocarpine preparations in heavily pigmented eyes: an evaluation of the influence of polymer vehicles on corneal penetration, drug availability, and duration of hypotensive activity.

Heavily pigmented eyes have been shown to be relatively resistant to pilocarpine, and present special problems in management of open-angle glaucoma. Studies have suggested that the hypotensive effect of pilocarpine may be influenced by the vehicle; therefore, 13 relatively resistant black patients (26 eyes) were selected for a clinical comparison of pilocarpine as delivered in two different polymer vehicles. One vehicle was composed of 1.67% polyvinylpyrrolidone and BP water-soluble polymers (Adsorbobase); the other of hydroxypropyl methylcellulose 0.5%. All patients had been under treatment with the pilocarpine/methylcellulose preparation; 20 of the 26 eyes were judged to be uncontrolled (IOP above 21 mm Hg). Control of intraocular pressure was promptly obtained with the pilocarpine/Adsorbobase solution, and maintained at lower pilocarpine concentrations than with the previous therapy. Often, frequency of instillation could be decreased. This clinical comparison suggests that the Adsorbobase vehicle appreciably enhances corneal penetration and availability of pilocarpine. Three cases are discussed demonstrating the need for titration when instituting a new therapy with as little as one fourth the concentration of the previous pilocarpine therapy.