Latanoprost: new preparation. Antiglaucoma eye drops that can change the colour of the iris

(1) Latanoprost, a prostaglandin F2 alpha analogue, is an antiglaucoma drug. (2) The clinical file is fairly thorough. (3) Dose-finding studies show that the optimal daily dose is a single drop of 0.005% solution, preferably in the evening. Two drops a day are less effective than one drop a day. (4) The local hypotensive action of latanoprost persists in the long term (current follow-up one year). (5) Four double-blind trials have compared 0.005% latanoprost eye drops and 0.5% timolol eye drops. In three trials the effect of latanoprost on intraocular pressure was statistically stronger than that of timolol. However, the difference in mean intraocular pressure was less than 2 mm Hg between the two treatments, and the clinical relevance of such a difference is not known. (6) Latanoprost has not been compared with the other available antiglaucoma eye drops. (7) Various trials have shown that intraocular pressure is statistically lower when latanoprost is combined with another antiglaucoma eye drop preparation (timolol, pilocarpine or dipivefrine) than during monotherapy. The additive action of latanoprost eye drops when combined with oral acetazolamide has been established more soundly in a comparative double-blind trial. (8) In approximately 30% of cases (especially patients with non homogeneous eye colour), latanoprost eye drops can cause permanent darkening of the iris. Patients must be warned of this risk before beginning treatment.