Intraocular pressure lowering effect of once daily versus once weekly latanoprost instillation in the same normal individuals.

This study tested whether once weekly instillation of latanoprost exerts the similar IOP lowering effect as once daily instillation in the same individuals. Latanoprost was administered on right eyes of eight healthy male volunteers once daily first for 24 days, which was followed by the 31-day washout and the subsequent once weekly instillation for another 24 days. The mean baseline IOP was 12.06 +/- 1.50 (range, 10.0 to 14.0) mmHg, whereas the mean IOP during once daily treatment was 9.87 +/- 1.71 mmHg, which was significantly lower than the former (p=0.025). The mean washout IOP was 12.56 +/- 2.16 mmHg, which was similar to the baseline IOP. The mean IOP during once weekly instillation of latanoprost was 11.34 +/- 1.51 mmHg, which was not statistically different from the washout IOP. Four of the 8 subjects showed 15% or more reduction in IOP both during once daily and once weekly instillations, two of whom were overlapped. Since the magnitude of the IOP reduction with once daily use was higher than that with once weekly use even in the responders, the current protocol of once daily instillation should be respected.