[Additive effect of timolol and the local carbonic anhydrase inhibitor MK-417 (sezolamide)]

MK-417 (sezolamide) is a topically active carbonic anhydrase inhibitor. The effect of additional treatment with sezolamide 1.8% twice daily to patient already receiving timolol 0.5% twice daily was investigated. For this purpose, 12-h diurnal curves were used in a double-masked, randomized, placebo-controlled, parallel study in 36 patients with bilateral primary open angle glaucoma or ocular hypertension who during beta blocker therapy had intraocular pressures (IOP) greater than or equal to 22 mmHg. For 15 days patients received sezolamide or placebo 10 min after 0.5% timolol given at 8 a.m. and 8 p.m. On treatment day 15, this addition of sezolamide twice daily induced a further mean decrease in IOP of approximately 4 mm Hg (about 15%) at 1, 2 and 4 h and of approximately 2-3 mm Hg at 0, 6, 8, 10 and 12 h after drug administration, thus demonstrating a partial additive effect of sezolamide and timolol. Thus, sezolamide may be a useful addition to the treatment of glaucoma in patients not adequately controlled by beta blocker therapy.