The eVect on intraocular pressure of latanoprost once or four times daily

Aims—To compare the eVect on intraocular pressure (IOP) of latanoprost applied once daily with four times daily and to study if the diVerence persisted when treatment changed to once daily. Methods—IOP was followed in 28 healthy volunteers in a double masked randomised 52 day study. Latanoprost 50 μg/ml was administered once daily in one eye and four times daily in the other during 2 weeks. Subsequently both eyes received one daily drop for 2 weeks. After another 3 weeks without treatment, a single drop was instilled in each eye. Results—The IOP reduction on days 2 and 3 was greater in the eyes treated with four daily doses (p<0.01). During the following period there were no statistically significant diVerences between the eyes. After 3 weeks without treatment the IOP was lower than pretreatment (p<0.001). A single dose of latanoprost on day 50 resulted in a similar decrease in IOP in both eyes. Transient photophobia, mild flare, and/or a few cells occurred in 15 subjects. Two subjects were withdrawn because of photophobia and/or signs of anterior uveitis. Conclusion—Latanoprost four times daily caused an IOP reducing eVect which was similar to once daily dosing, except for the first 2 days of treatment when it was more eVective. Transient photophobia, cells, and flare were common during the four dose regimen, but resolved spontaneously without cessation of treatment. (Br J Ophthalmol 2001;85:1163–1166) Latanoprost is a prostaglandin F2á (PGF2á) analogue developed for glaucoma treatment. It has a potent ocular hypotensive eVect in humans. Its main mechanism of action is on uveoscleral outflow. 5 It has been shown that twice daily dosing of latanoprost has less ocular hypotensive eVect than once daily. Although the initial eVect on the intraocular pressure (IOP) with twice daily application is more pronounced than with once daily applications there is a loss of eVect with twice daily applications during the first week. The mechanism behind this loss of eVect is not clear, and we decided to determine if an even more frequent administration of latanoprost would result in further loss of the eVect on IOP. Thus the aim of this study was to compare the eVect on IOP of latanoprost applied once daily in one eye with latanoprost applied four times daily in the other eye. A secondary aim was to investigate if any diVerence between the two treatment arms was persisting if the treatment was changed to one daily drop and if such a diVerence could be recalled by a single dose of latanoprost after 3 weeks without treatment. Materials and methods