Initial and long-term effects of metoprolol and timolol on the intraocular pressure. A comparison in healthy subjects.

The effect of 3% metoprolol and 0.5% timolol eye drops on the intraocular pressure (IOP) was compared in healthy subjects. The effect of a single dose was determined up to 48 h after administration of the drug before and after 2 weeks' treatment twice daily with the test drug. The study was performed as a randomized, double-masked cross-over study. Both drugs caused significant reductions in IOP with a maximal effect 2 to 8 h after administration of the drug. Timolol reduced the mean IOP from 14.8 to 10.7 mmHg after 2 h. The corresponding figures for metoprolol were 14.1 and 11.5 mmHg. There was no clear cut effect in the untreated eye for either drug. The effect of one drop timolol lasted for at least 48 h. The duration of one drop metoprolol was 36 h, but there was a marked reduction of the effect between 8 and 12 h after administration of the drug. Both drugs caused a smaller pressure reduction when the effect of one drop was followed for 48 h after to weeks' treatment compared to the initial response. This "escape" was of the same order for both drugs. It has been concluded that the composition of metoprolol eye drops used in the present study is less efficient than timolol as an ocular hypotensive agent.