Carbonic anhydrase inhibitors reduce intraocular pressure by partially suppressing the secretion of aqueous humor (inflow), although the mechanism by which they do this is not fully understood. Evidence suggests that HCO3- ions are produced in the ciliary body by hydration of carbon dioxide under the influence of carbonic anhydrase and diffuse into the posterior chamber which contains more Na+ and HCO3- ions than does plasma and consequently is hypertonic. Water is attracted to the posterior chamber by osmosis. Systemic administration of a carbonic anhydrase inhibitor has been shown to inactivate carbonic anhydrase in the ciliary body of the rabbit†s eye and to reduce the high concentration of HCO3- ions in ocular fluids. As is the case with all carbonic anhydrase inhibitors, DARANIDE in high doses causes some decrease in renal blood flow and glomerular filtration rate.

In man, DARANIDE begins to act within an hour and maximal effect is observed in two to four hours. The lowered intraocular tension may be maintained for approximately 6 to 12 hours.

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