The effect of adding prostaglandin F2 alpha-isopropylester to timolol in patients with open angle glaucoma.

Prostaglandin F2 alpha-isopropylester (PGF2 alpha-IE) (0.5 microgram) or placebo was added twice daily for 1 week to one eye in each of 30 patients with open angle glaucoma not adequately controlled with timolol treatment. Compared with placebo, PGF2 alpha-IE reduced the intraocular pressure of these timolol-treated eyes significantly. The absolute difference in mean change between PGF2 alpha-IE and placebo groups was 4.5 mm Hg with a 95% confidence interval of 3.1 to 6.6 mm Hg, corresponding to a mean reduction of initial intraocular pressure of 17.4% in eyes treated with PGF2 alpha-IE. Conjunctival or episcleral hyperemia was seen in all eyes treated with PGF2 alpha-IE for up to 4 hours but not in eyes treated with timolol and placebo, and aqueous flare was not observed in any eye. Thirteen of 15 patients treated with PGF2 alpha-IE, compared with only 3 of 15 who received placebo, reported mild to moderate subjective discomfort in the treated eye in the form of a foreign-body sensation that lasted for up to 2 hours. These results demonstrate that PGF2 alpha-IE, in a dose that has previously been shown to reduce intraocular pressure in normotensive volunteers or in patients with glaucoma who are taking no other medications, also significantly reduces the intraocular pressure of patients with glaucoma whose pressures are not adequately controlled on a twice-daily regimen of timolol.