Purpose: To compare the additional intraocular pressure-lowering effect of latanoprost 0.005% administered once daily with that of pilocarpine 2% administered three times daily in patients with primary open-angle glaucoma or ocular hypertension currently on monotherapy with timolol 0.5% twice daily.
Methods: In a 6-month, multicenter, randomized, open-label study 242 patients with POAG or OH whose IOP was not controlled with timolol 0.5% b.i.d. were enrolled. Eyes had not been treated with pilocarpine and latanoprost for at least 2 years. An analysis of covariance with diurnal IOP change from baseline to month 6 for study eyes was performed.
Results: Four patients on latanoprost 0.005% and 35 on pilocarpine 2% did not complete the study (P<0.001). Two hundred and forty patients were included in the intent-to-treat analysis. For both treatments the diurnal IOP reduction after 6 months was statistically significant (P<0.001). IOP (mean+/-SD) was reduced from 23.3+/-2.8 to 17.8+/-2.8 (-5.6) mmHg in the latanoprost 0.005% group and from 23.0+/-3.2 to 18.5+/-2.4 (-4.8) mmHg in pilocarpine 2% t.i.d.-treated eyes. The mean difference of -0.8 mmHg (per protocol, PP) and -1.6 mmHg (intend-to-treat, ITT) was statistically significant (P<0.04, PP; P<0.001, ITT) in favor of latanoprost 0.005%. Two eyes treated with latanoprost showed an iris color change. Thirty-six patients in the latanoprost group and 106 in the pilocarpine 2% group reported ocular adverse events (P<0.001).
Conclusion: From the data we conclude that the additivity of latanoprost 0.005% is at least as effective as pilocarpine 2% t.i.d. in reducing IOP when added to eyes currently on monotherapy with timolol 0.5% b.i.d. Latanoprost was better tolerated than pilocarpine 2% eye drops in this study. The increase in iris pigmentation requires further investigation.