Effect of atenolol and metoprolol on the anticoagulant activity of acenocoumarin.

In patients receiving long-term acenocoumarin treatment, the effect on anticoagulant activity of atenolol (100 mg once-daily) and metoprolol (100 mg twice daily) was compared in a randomised within-patient open trial. No significant differences were demonstrated between mean prothrombin time and Thrombotest during treatment with atenolol, metoprolol or placebo. These data do not suggest the existence of an interaction between acenocoumarin and the moderately lipophilic beta-adrenoceptor blocker metoprolol, or the hydrophilic beta-adrenoceptor blocker atenolol. The results are discussed in the light of published data for the highly lipophilic beta-adrenoceptor blocker propranolol.