A comparison of the ocular hypotensive efficacy of twice-daily 0.25% levobunolol to 0.5% timolol in patients previously treated with 0.5% timolol

Treatment with noncardioselective beta-adrenoceptor antagonists (e.g., 0.5% timolol or 0.5% levobunolol) is standard practice for lowering elevated intraocular pressure (IOP). However, because there are risks and side effects associated with the use of these agents, a lower, yet still effective, dose may be preferred. We gave 0.5% timolol twice daily for 30 days to 143 patients. In a double-masked, randomized fashion, we then assigned patients to continue to receive 0.5% timolol twice daily or 0.25% levobunolol twice daily for 8 weeks. The mean unmedicated baseline IOP for both groups was approximately 25 mm Hg. After 30 days of timolol pretreatment, the mean IOP in both groups decreased to approximately 19 mm Hg (p = 0.210). After the 30-day timolol pretreatment period, and subsequent randomization to either 0.5% timolol or 0.25% levobunolol treatment, there was little change in overall mean IOP (0.03 mm Hg decrease for levobunolol, 0.06 mm Hg increase for timolol; p = 0.811) from the timolol pretreatment baseline. One patient assigned to the timolol treatment group was terminated from the study due to inadequate control of IOP. We conclude that the mean IOP lowering effect of 0.25% levobunolol is equivalent to 0.5% timolol, and switching patients from twice-daily 0.5% timolol to twice-daily 0.25% levobunolol poses no significant risk of decreased ocular hypotensive efficacy.