Effect of MK-507 on aqueous humor dynamics in normal human eyes.

The effects of the topical carbonic anhydrase inhibitor, MK-507, on aqueous humor dynamics were studied in 6 normal volunteers. As a baseline study, intraocular pressure (IOP) was determined and aqueous protein concentration was checked hourly by laser flare-cell photometry from 0900 to 1800 hours. One week later, IOP and aqueous protein concentration were determined in the same subjects on the same time schedule with instillation of 1% MK-507 at 1100 hours. After one more week, the same experiment was carried out with oral administration of acetazolamide at a dose of 250 mg at 1100 hours. Topical MK-507 showed the maximum IOP reduction at 3 hours and increased aqueous protein concentration reaching its maximum at 4 hours. Oral acetazolamide showed the maximum IOP reduction at 2 hours and the maximum increase in aqueous protein concentration was at 3 hours. Although the peak effect on IOP or aqueous protein concentration did not significantly differ between topical MK-507 and oral acetazolamide, only oral acetazolamide showed a significant effect at 1 hour. These results suggested that topical MK-507 reduced the aqueous humor production, but it took more time for the ocular effect to become manifest than after administration of oral acetazolamide.