AQUEOUS-HUMOR FLOW IN HUMAN EYES TREATED WITH DORZOLAMIDE AND DIFFERENT DOSES OF ACETAZOLAMIDE

Objective: To measure the effect of topically applied 2% dorzolamide h ydrochloride (Trusopt, Merck Gs Co Inc, Whitehouse Station, NJ) and di fferent doses of orally administered acetazolamide (Diamox, Lederle Op hthalmic Pharmaceuticals, Pearl River, NY), alone and in combination, on aqueous humor flow. Design: A randomized, double-masked, placebo-co ntrolled study of 20 human subjects was carried out. Aqueous humor flo w was measured by clearance of topically applied fluorescein. Serum st andard bicarbonate and serum acetazolamide levels were analyzed. Resul ts: Treatment with dorzolamide reduced aqueous flow by 17%, and a maxi mum dose of acetazolamide alone reduced flow by 29%. Increasing doses of acetazolamide alone gradually decreased flow, while small doses of acetazolamide did not suppress flow further when dorzolamide was alrea dy applied topically. Serum acetazolamide concentrations rose with inc reasing doses of acetazolamide. Serum standard bicarbonate levels were all in the normal range. Conclusions: Treatment with dorzolamide redu ced aqueous humor flow Statistically significantly (2.50 mu L/min vs 3 .00 mu L/min; P=.001) compared with placebo, but less than a maximum d ose of acetazolamide; Small doses of acetazolamide added to dorzolamid e treatment did not further enhance the decrease in flow. Since there was no metabolic acidosis as measured by plasma levels of standard bic arbonate, the decrease in aqueous flow could be attributed to the dire ct action of the carbonic anhydrase inhibitors on the carbonic anhydra se enzymes, It is concluded that the smaller effect of dorzolamide, as compared with acetazolamide, is due to insufficient inhibition of at least 1 of the 2 carbonic anhydrase isozymes involved in aqueous humor production.