Interaction of pilocarpine with latanoprost in patients with glaucoma and ocular hypertension

Purpose: To study any interaction between pilocarpine and latanoprost when administered together, and to determine the optimal timing of dosage to max imize reduction of intraocular pressure (IOP). Methods: Nineteen adult patients with either primary open-angle glaucoma or ocular hypertension participated in a single-center, prospective case stud y with masked observer. After a baseline measurement of IOP during treatmen t with latanoprost was obtained, initial treatment with pilocarpine three t imes daily was added without bedtime administration. This was followed by t hree different dose regimens in which pilocarpine was administered four tim es daily, altering the bedtime pilocarpine dose to precede the latanoprost dose by 1 hour, or to follow it by 10 minutes or 1 hour. Intraocular pressu re was measured at 8:00 AM and 75 minutes after administration of the morni ng dose of pilocarpine. Results: Comparison of IOP at 8:00 AM with baseline showed no significant c hange when pilocarpine was taken three times daily, or when pilocarpine was taken four times daily when the bedtime dose preceded administration of la tanoprost by 1 hour. There were significant decreases in IOP versus baselin e when the bedtime dose of pilocarpine was taken simultaneously with or 1 h our after administration of latanoprost. Application of pilocarpine immedia tely after the 8:00 AM IOP measurement revealed a significant additional de crease in pressure. There were no significant differences between dosage sc hedules in the magnitude of the additional reduction in IOP. Conclusion: The order and timing of administration of pilocarpine and latan oprost can significantly alter their ocular hypotensive activity. Pilocarpi ne is most effective when administered four times daily, and when the bedti me dose is administered 1 hour after administration of latanoprost.