[Local carbonic anhydrase inhibitors MK-927 and Mk-417. Effect and tolerance]

A comparative ocular tolerance study was undertaken with the topical carbonic anhydrase inhibitor (CAI) MK-927 (1% and 2%) and its S-enantiomer MK-417 (1% and 1.8%) in 20 healthy normal volunteers. In this randomized, double-blind cross over study, placebos were used for control over five periods. The subjects received one drop of placebo (common vehicle) or CAI in each eye in successive periods separated by a washout period of 1 week. Three hours after the dose, the IOP was found to be decreased by 5.3% to 9.1%, depending on the dose, with all four CAI treatments and significantly so with MK-417. Pupil-size and central vision were unchanged by CAIs. External and anterior segment examination revealed no changes following any of the treatments. The incidence of burning was significantly increased by 2% MK-927 (p less than 0.01) and 1.8% MK-417 (p less than 0.05) compared to placebo. The mean duration of burning placebo was 16.8 s, but it was significantly longer (23 to 37.1 s) following CAI application. Duration of tearing following CAI application was also significantly prolonged (p less than 0.05).