Comparison of twice-daily and three-times-daily dosing of dorzolamide in ocular hypertension and primary open-angle glaucoma patients treated with latanoprost

Introduction

Clinically, dorzolamide (Trusopt®; Merck &; Co Inc, West Point, PA, USA) is often used twice daily (b.i.d.) or three times daily (t.i.d.) as adjunctive therapy with prostaglandins. Our purpose was to determine the effect of dorzolamide on intraocular pressure (IOP) when added to latanoprost (Xalatan®; Pfizer Inc, New York, NY, USA) baseline treatment, and to evaluate potential efficacy differences between b.i.d. and t.i.d. dosing of dorzolamide.

Methods

This was a prospective, randomised, two-period crossover trial in ocular hypertensive or primary open-angle glaucoma patients (29 eyes in 15 patients) with an IOP of > 20 mmHg on latanoprost baseline treatment. Patients were randomly assigned to b.i.d. (08.00 and 20.00) or t.i.d. (08.00, 16.00 and 20.00) dosing of dorzolamide, treated in both eyes for 4 weeks, washed out for 3 weeks, then switched to the opposite dosing frequency for 4 weeks. Diurnal IOP measurements (every 2 hours from 08.00 to 20.00) were performed at baseline and at the end of treatment periods.

Results

The mean baseline IOP was 20.9±0.6 mmHg. After b.i.d. and t.i.d. dosing, the mean IOP was 17.7±0.6 mmHg (13.5% reduction) and 17.8±0.8 mmHg (16.5% reduction), respectively (both P<0.001 compared with baseline IOP). Diurnal IOP control was similar in the two groups, although mean IOP reduction was significantly lower at 18.00 on the t.i.d. regimen (4.7±3.3 mmHg) than with the b.i.d. regimen (2.3±2.7 mmHg, P=0.038). At other time points, no significant differences between the groups were observed.

Conclusion

Dorzolamide 2% added to latanoprost 0.005% baseline treatment caused a significant decrease in IOP. The b.i.d. versus t.i.d. dosing of dorzolamide did not significantly affect a change in IOP except at one afternoon time point.