A clinical trial of MK-507, Trusopt, for raised intraocular pressure - The Australian Experience

Background: Since the introduction of carbonic anhydrase inhibitors, a topical preparation has been sought to avoid the complications of systemic medication while retaining the effect of lowering intraocular pressure. Recently, a topical carbonic anhydrase inhibitor, MK-507, has been found superior to others and introduced for multicentre clinical trial.
Patients and methods: As part of an international rnulticentre trial, we compared MK-507 with beta blockers for one year in 20 patients with raised intraocular pressure, both as monotherapy and in combination.
Results: Twelve patients with a mean peak pressure of 31.9 ± 6.8 mmHg (range, 22 to 49 mmHg) off all medication received MK-507. After two weeks, mean peak pressure was 24.7 ± 6.1 mmHg (range, 14 to 41 mmHg) — a 22.6% fall in pressure. Six of these patients had a mean peak pressure of 27.8 ± 6.4 mmHg (range, 21 to 41 mmHg), a fall of 19.2% from day one and were given timolol as add-on therapy. This resulted in a fall to 19.1 ± 2.8 (range, 15 to 24 mmHg) at year one, a fall of 31.3% after add-on. Four patients on timolol and four on betaxolol gave similar falls in pressure with an additional fall when MK-507 was used as add-on therapy.
Conclusions: MK-507 demonstrated its effectiveness as an ocular hypotensive agent in this trial of patients with an unusually high rise in pressure. It showed a hypotensive effect roughly equivalent to beta blockers. It is likely that either a topical carbonic anhydrase inhibitor or a cardioselective beta blocker will be the medication of first choice in newly diagnosed glaucoma.