Cardiovascular Effects of Ophthalmic Timolol

Abstract

We studied cardiovascular effects related to ophthalmic timolol maleate, a beta-adrenergic blocker commonly used to treat chronic glaucoma. Twenty normal subjects were randomly assigned to two double-blind treatment groups each with ten subjects. One group received two drops of ophthalmic timolol (0.5%) twice daily for 4 weeks, and the other received two drops of placebo (artificial tears) twice daily for 4 weeks. Ophthalmic timolol significantly decreased resting and maximal exercise heart rate after the first dose and maximal exercise heart rate during chronic dosing. Chronic timolol administration reduced oxygen consumption at maximal exercise and blunted the augmentation in exercise capacity seen during chronic placebo therapy. Cardiac sympathetic tone and inotropy were reduced after ophthalmic timolol treatment. Despite the presence of drug-induced cardiovascular effects, the plasma levels of timolol were often undetectable and never exceeded 2.8 ng/mL.