Effects of Acetazolamide on Choroidal Blood Flow

Abstract

Background and Purpose-The acetazolamide provocation test is commonly used to study cerebrovascular vasomotor reactivity. On the basis of the effect of a carbonic anhydrase inhibitor in the central nervous system, we hypothesized that acetazolamide may also increase blood flow in the human choroid. Methods-In a placebo-controlled, randomized, double-blind, three-way crossover design, acetazolamide (500 mg or 1000 mg IV) or placebo was administered to nine healthy subjects. The effect of acetazolamide was studied at 15-minute intervals for 90 minutes. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation. In addition, mean blood flow velocity and resistive index in the ophthalmic artery were measured with Doppler sonography. In a second study in six healthy subjects, we assessed the effect of acetazolamide (1000 mg IV) on intraocular pressure. Results-Acetazolamide increased fundus pulsation amplitude in a dose-dependent manner (1000 mg: ϩ33%; 500 mg: ϩ20%; PϽ0.001, ANOVA). The effect of acetazolamide on MFV (1000 mg: ϩ18%; 500 mg: ϩ8%; Pϭ0.003, ANOVA) and RI (1000 mg: Ϫ4%; 500 mg: Ϫ2%; Pϭ0.006, ANOVA) was less pronounced but also significant. Acetazolamide did not induce any changes in systemic hemodynamic parameters but significantly decreased intraocular pressure (1000 mg: Ϫ37%; PϽ0.0001). Conclusions-The present data show for the first time that intravenously administered acetazolamide increases choroidal blood flow in humans. This phenomenon therefore indicates that the acetazolamide provocation test may qualify as a tool to investigate ocular vasomotor reactivity in a variety of ocular diseases. Moreover, the increase in choroidal blood flow after carbonic anhydrase inhibition can be expected to contribute to the therapeutic efficacy of carbonic anhydrase inhibitors in glaucoma. (Stroke. 1998;29:997-1001.)

Carbonic anhydrase inhibitors and ventilation: a complex interplay of stimulation and suppression

“…At this time, very little is known about CA and brain blood flow regulation, or whether vascular smooth muscle contains CA. Although a global increase in baseline cerebral blood flow occurs with very high-dose CA inhibitors [33,34], this was not observed with the more conventional doses used clinically [35] or in the present study by WAGENAAR et al [2]. However, given the very high ventilatory sensitivity to CO 2 , even small changes in global and regional brain blood flow may be important.…”

Indomethacin lowers optic nerve oxygen tension and reduces the effect of carbonic anhydrase inhibition and carbon dioxide breathing

“…6 Carbonic anhydrase inhibitors (CAIs) elevate ONPO 2 in pigs 7 but the mechanism of action is not known. Systemic administration of CAI causes carbon dioxide (CO 2 ) accumulation in blood and tissue, 8 known to increase cerebral blood flow.…”

Evaluation of Choroidal Thickness in Patients with Primary Open Angle Glaucoma and Pseudoexfoliation Glaucoma

“…Literatürde antiglokomatöz ajanların koroid kalınlığını etkilediğini gösteren çalışmalar olduğu gibi, etkilemediğini gösteren çalışmalar da vardır. [30][31][32] Antiglokomatöz ilaçlardan topikal alfa-2 agonistleri, asetazolamid ve dorzolamid gibi ajanların koroidal kalınlığı etkileyen koroidal kan akımını artırdık-ları gösterilmiştir. 30,31 Fakat Maul ve ark., glokomlu hastalarda koroid kalınlığını etkileyen faktörleri araştırdıkları çalışmalarında, antiglokomatöz ajanların koroid kalınlığını etkilemediğini belirtmişlerdir.…”

“…[30][31][32] Antiglokomatöz ilaçlardan topikal alfa-2 agonistleri, asetazolamid ve dorzolamid gibi ajanların koroidal kalınlığı etkileyen koroidal kan akımını artırdık-ları gösterilmiştir. 30,31 Fakat Maul ve ark., glokomlu hastalarda koroid kalınlığını etkileyen faktörleri araştırdıkları çalışmalarında, antiglokomatöz ajanların koroid kalınlığını etkilemediğini belirtmişlerdir. 32 Glokom gruplarında görme alanı ortalama deviasyon açısından bir farklılık olmasa da, glokomatöz hasarın şiddetini gösteren retina sinir lifi tabaka kalınlığı ile koroid kalınlı-ğının ilişkisinin değerlendirilmemesi çalışmamı-zın bir başka eksik yönüdür.…”