EFFECTS OF ACETAZOLAMIDE ON CHOROIDAL BLOOD-FLOW

Background and Purpose-The acetazolamide provocation test is commonly used to study cerebrovascular vasomotor reactivity. On the basis of th e effect of a carbonic anhydrase inhibitor in the central nervous syst em, we hypothesized that acetazolamide may also increase blood flow in the human choroid. Methods-In a placebo-controlled, randomized, doubl e-blind, three-way crossover design, acetazolamide (500 mg or 1000 mg IV) or placebo was administered to nine healthy subjects. The effect o f acetazolamide was studied at 15-minute intervals for 90 minutes, Pul satile choroidal blood flow was assessed with laser interferometric me asurement of fundus pulsation. In addition, mean blood flow velocity a nd resistive index in the ophthalmic artery were measured with Doppler sonography. In a second study in six healthy subjects, we assessed th e effect of acetazolamide (1000 mg IV) on intraocular pressure. Result s-Acetazolamide increased fundus pulsation amplitude in a dose-depende nt manner (1000 mg: +33%; 500 mg: +20%; P<0.001, ANOVA). The effect of acetazolamide on MFV (1000 mg: +18%; 500 mg: +8%; P=0.003, ANOVA) and RI (1000 mg: -4%; 500 mg: -2%; P=0.006, ANOVA) was less pronounced bu t also significant. Acetazolamide did not induce any changes in system ic hemodynamic parameters but significantly decreased intraocular pres sure (1000 mg: -37%; P<0.0001). Conclusions-The present data show for the first time that intravenously administered acetazolamide increases choroidal blood flow in humans. This phenomenon therefore indicates t hat the acetazolamide provocation test may qualify as a tool to invest igate ocular vasomotor reactivity in a variety of ocular diseases. Mor eover, the increase in choroidal blood flow after carbonic anhydrase i nhibition can be expected to contribute to the therapeutic efficacy of carbonic anhydrase inhibitors in glaucoma.