Tolerability and efficacy of dorzolamide versus acetazolamide added to timolol

Evaluate the safety and efficacy of dorzolamide versus acetazolamide when added to once daily 0.5% timolol maleate ophthalmic gel forming solution (timolol gel).

This was a randomized, double-masked, multicenter, active-controlled, parallel group study of 215 patients with open-angle glaucoma or ocular hypertension. Following a two-week treatment period with timolol gel, patients with IOP > or = 22 mm Hg and who tolerated one week of acetazolamide 250-mg q.i.d. either were randomized to acetazolamide or dorzolamide 2% three times daily for 12 weeks.

In 155 randomized patients (dorzolamide, N = 80, acetazolamide, N = 75), compared to the dorzolamide, acetazolamide had a statistically greater number of systemic adverse events (dorzolamide 50%, acetazolamide 75%, p = 0.001), adverse events associated with carbonic anhydrase inhibitor (CAI) therapy (dorzolamide 26%, acetazolamide 53%, p < 0.001) and discontinuations due to CAI adverse experiences (dorzolamide 8%, acetazolamide 24%, p = 0.007). Intent to treat analysis found that changes from baseline in IOP were similar at both troughs (dorzolamide 1.4 +/- 0.46 mm Hg, acetazolamide 0.8 +/- 0.47 mm Hg, p = 0.386). However, per-protocol analysis found statistically improved pressure control with acetazolamide (0.1 +/- 0.42 mm Hg) compared to dorzolamide (1.9 +/- 0.43 mm Hg) (p = 0.009).

This study found a greater incidence of systemic and CAI adverse experiences and discontinuations due to acetazolamide compared to dorzolamide.