Identification of isoenzyme C as the principal carbonic anhydrase in human ciliary processes.

Carbonic anhydrase was extracted from the excised processes of the ciliary bodies of 10 pairs of enucleated human eyes, and the isoenzyme composition was assayed by measuring the degree of inhibition produced by acetazolamide at two standard concentrations. Also, the effect of incubating with iodoacetate was determined in two pairs of these eyes. Only isoenzyme C was detected. Accordingly, it seems that differences in reduction of intraocular pressure that are common among patients treated for glaucoma with systemic carbonic anhydrase inhibitors, despite uniform serum concentrations, are not attributable to interindividual variation of carbonic anhydrase isoenzymes in the ciliary processes.

Acetazolamide dosage forms in the treatment of glaucoma.

Patients with chronic glaucoma had a carefully scheduled series of intraocular pressure measurements before and after taking acetazolamide for one week at the following dosages: none, 500 mg of sustained-release capsules once a day, 500 mg of capsules twice a day, and 250 mg of tablets four times a day. A capsule taken once a day, which is better tolerated than one taken twice a day by some patients, offers a substantial pressure-lowering effect that lasts at least 23 hours, although the magnitude of the pressure lowering is less than with higher dosages. One capsule twice a day appears to be as effective in the regulation of IOP as one tablet four times a day. The 45% reduction in outflow pressure is achieved with an acetazolamide serum concentration in the range of 15 to 20 micrograms/mL.