EFFECTS ON INTRAOCULAR-PRESSURE AND SIDE-EFFECTS OF 0.005-PERCENT LATANOPROST APPLIED ONCE-DAILY, EVENING OR MORNING - A COMPARISON WITH TIMOLOL

Purpose: To compare the effect on intraocular pressure (IOP) and side effects of 0.005% latanoprost applied once daily, morning or evening, with 0.5% timolol applied twice daily. Methods: A 6-month randomized, double-masked, multicenter study with three parallel groups was undert aken. Two hundred sixty-seven patients were randomized, 84 to timolol, 89 to latanoprost in the morning for 3 months and then in the evening for another 3 months, and 94 to latanoprost with the treatment schedu le reversed. Results: After 6 months, timolol reduced diurnal IOP from 24.6 to 17.9 mmHg (27%); latanoprost applied in the morning, from 25. 5 to 17,7 mmHg (31%); and latanoprost applied in the evening, from 24. 8 to 16.2 mmHg (35%), The efficacy of latanoprost applied in the eveni ng was statistically superior to latanoprost applied in the morning an d to timolol (P < 0.001). Latanoprost induced a slight increase in con junctival hyperemia in 31.4% of treated patients, compared with 15.9% for timolol. Sporadic episodes of mild punctate corneal epithelial ero sions were three times as frequent in latanoprost-treated eyes as in t imolol-treated eyes. The most significant ocular side effect was incre ased pigmentation of the iris observed in five and suspected in seven more latanoprost-treated eyes, All these eyes had a mixed green-brown or blue/gray-brown iris color. Timolol reduced heart rate by 3 beats/m inute (P < 0.005), Conclusions: The effect on diurnal IOP of latanopro st applied once daily in the evening is superior to that of timolol. T he main difference in side effects is increased pigmentation of the ir is induced by latanoprost, most likely due to stimulation of melanogen esis in iris stromal melanocytes.