Sezolamide (previously known as MK-417), a potent carbonic anhydrase inhibitor capable of reducing intraocular pressure after topical application, was under investigation for the treatment of glaucoma. . Sezolamide is the more potent of the two stereo isomers of MK-927 in inhibiting human carbonic anhydrase isoenzyme II, the isoenzyme found in ciliary processes. Sezolamide, the S-enantiomer of MK-927, has demonstrated activity in vitro approximately 80 times that of the R-enantiomer of MK-927 (concentrations of 0.54 nmolll and 44 nM, respectively, inhibiting activity of human carbonic anhydrase isoenzyme II by 50%). Clinically, sezolamide has also demonstrated greater activity than MK-927 both after single-dose and after twice daily administration in patients.