Circadian intraocular pressure control with dorzolamide versus timolol maleate add-on treatments in primary open-angle glaucoma patients using latanoprost.

PURPOSE

To compare the 24-hour efficacy of dorzolamide and timolol maleate administered twice daily to primary open-angle glaucoma patients whose intraocular pressure (IOP) could not be adequately controlled with latanoprost monotherapy.

METHODS

In this double-blind prospective crossover clinical comparison trial, 36 primary open-angle glaucoma patients with uncontrolled IOP despite treatment with latanoprost applied once daily were administered timolol and dorzolamide twice daily. The treatment sequence was randomized. All patients underwent measurements for four 24-hour tonometric curves: at baseline and after each 4-week period of treatment. The IOP measurements were taken at 06:00, 09:00, 12:00, 15:00, 18:00, 21:00, 24:00 and 03:00 h. The between-group differences were tested for significance by means of parametric analysis of variance at each time point and circadian curve. The peak values within circadian curve were defined. The mean of the exact amount and percentage of additional IOP reductions from baseline were evaluated and success rates (a minimum of 10% reduction) were determined for both drug regimens.

RESULTS

The mean peak/circadian curve IOPs were 23.4 +/- 2.2/21.8 +/- 2.2 mm Hg at dorzolamide baseline, 23.3 +/- 2.2/21.7 +/- 2.1 mm Hg at timolol baseline, and reduced to 20.2 +/- 1.7/18.7 +/- 1.7 mm Hg and 20.7 +/- 2.4/19.4 +/- 1.6 mm Hg, respectively. When added to latanoprost, both dorzolamide and timolol lowered IOP at circadian curve significantly (p < 0.05). Dorzolamide reduced baseline IOP values at each time point. Timolol also significantly reduced baseline IOP values at all time points except at 03:00. The mean of the exact amount and percentage of reduction in IOP at circadian curve and 5 out of 8 time points were significantly greater with dorzolamide add-on treatment (p < 0.05). The successful reduction rates were 86% for the dorzolamide group and 61% for the timolol group (p = 0.016; chi(2) test).

CONCLUSION

Both of the combinations are effective in lowering IOP, the exact amount and percentage of reduction is greater with the latanoprost + dorzolamide regimen, especially at night-time.