A comparative study of two dose regimens of latanoprost in patients with elevated intraocular pressure

Objective: The purpose of the study was to determine whether latanoprost (13,14-dihydro-17-phenyl-18,19,20-trinor PGF(2a)-isopropyl ester), a new prostaglandin analogue that has been found effective in reducing intraocular pressure (IOP) in humans, is equally effective at lower concentrations than those currently employed. Design and Participants: Fifty patients with glaucoma or ocular hypertension were treated in a randomized, crossover, double-masked fashion with 1 drop of latanoprost (50 μg/ml once daily and 15 μg/ml twice daily) in the affected eye(s) for 3 weeks on each concentration. Tonometry was obtained at 8:00, 13:00, and 17:00 hours at baseline (untreated) and after 3 weeks on each concentration. Placebo (a buffer solution of latanoprost eye drop) was administered for complete masking of the study. Results: Mean baseline (untreated) diurnal IOP for the entire sample was 24.7 mmHg. Intraocular pressure was reduced by 6.1 mmHg with latanoprost 15 μg/ml twice daily, and by 7.5 mmHg with 50 μg/ml once daily. Results with both regimens were significant (P < 0.001 each, Student's t- test). However, the 50 μg/ml dose was significantly more effective than the 15 μg/ml dose, with a difference of 1.4 mmHg (P < 0.001, ANOVA). Both dose regimens were well tolerated, with little, predominantly mild, ocular discomfort. The higher dose did not cause more hyperemia at 3 weeks than the lower one, i.e., the lower dose yielded a slightly higher score (1.8 mm) on the visual analogue scale (P < 0.29, ANOVA). Conclusions: Latanoprost administered at a concentration of 50 μg/ml once daily effectively reduces lOP in patients with elevated IOP. Administration of a lower concentration (15 μg/ml) twice daily is less effective, but still significant.