The effects of timolol on intraocular pressure and exercise heart rate in poor and extensive debrisoquine metabolizers.

The effects of a single 20 mg oral dose of timolol, a non-selective beta-adrenoceptor antagonist which is subject to hydroxylation in the liver, on intraocular pressure and heart rate were compared in four poor and five extensive debrisoquine metabolizers, using non-contact tonometry and bicycle ergometry. The beta blockade of timolol on exercise heart rate was significantly higher in poor than in extensive metabolisers with no significant difference on resting heart rate or intraocular pressure.