Additive effect of dorzolamide or carteolol to latanoprost in primary open-angle glaucoma: a prospective randomized crossover trial

PURPOSE: To compare the additive effect of dorzolamide or carteolol to latanoprost on intraocular pressure (IOP) in glaucoma patients. DESIGN: Prospective open-label randomized crossover clinical study. METHODS: A total of 64 patients with primary open-angle glaucoma were treated with latanoprost 0.005% once daily for 3 months then randomized to receive latanoprost plus dorzolamide 1% 3 times daily (dorzolamide preceding group; n=32) or carteolol hydrochloride 2% twice daily (carteolol preceding group; n=32) for a further 3 months. Then, all patients were crossed over to the opposite treatment arm for a further 3 months. IOP was recorded each month at around the time same as on the baseline day. RESULTS: Sixty-one patients (95%) completed this trial. In the dorzolamide preceding group, mean (+/-SD) IOP was 19.0+/-2.1 mm Hg at baseline and 16.0+/-2.1 mm Hg at the end of latanoprost monotherapy (P<0.01). Addition of dorzolamide reduced IOP to 15.0+/-1.3 mm Hg and this was not changed by switching to carteolol (15.1+/-1.7 mm Hg). In the carteolol preceding group, IOP was 19.1+/-1.9 mm Hg at baseline and 16.2+/-1.2 mm Hg at the end of latanoprost monotherapy (P<0.01). Addition of carteolol reduced IOP to 14.9+/-1.5 mm Hg, and after switching to dorzolamide IOP was 15.2+/-1.5 mm Hg. Mean additional IOP reduction was 0.9+/-1.2 mm Hg (5.6%) for the latanoprost-dorzolamide combination and 1.1+/-1.5 mm Hg (6.8%) for the latanoprost-carteolol combination. Hence, IOP reduction by carteolol and dorzolamide additionally to latanoprost was not different. CONCLUSIONS: Both dorzolamide and carteolol reduce IOP additively when used in combination with latanoprost, and the additive effect of these drugs is equal.