A cross-over trial comparing once daily levobunolol with once and twice daily timolol.

The intraocular pressure (IOP) lowering efficacy of once-daily levobunolol 0.5% was compared with timolol 0.5% twice-daily and timolol 0.5% once-daily in 20 chronic open angle glaucoma and 5 ocular hypertensive patients. The design used was a randomised double blind cross-over trial with three periods each of 8 weeks separated by 2 weeks of no treatment. We found that following levobunolol a two week washout was not sufficient for the IOP to return to its original baseline level suggesting that levobunolol is a longer acting drug than timolol. Adjusting for this carryover effect, we found on significant difference in the IOP lowering effect among the three regimes (p = 0.53). Reduced cost, less ocular discomfort and better compliance are the main potential advantages of the once daily treatments.