J Clin Pathol 1989;42:793-796 Lack of significant effect of therapeutic propranolol on measurable platelet function in healthy subjects

suMM:ARY Propranolol, a non-selective,B blocker, was administered orally in therapeutic doses. The effects of a single dose (160 mg) and one week's treatment (80 mg twice a day) on platelet function were compared in healthy young subjects. There were no significant changes in circulating platelet aggregates, template bleeding time, platelet factor 3 availability and thromboxane f2 (TXP2) generation. Platelet aggregation responses as assessed by angle of slope and maximal percentage aggregation (all agonists) and lag phase (collagen) showed no changes of biological importance, although minor changes reaching significance were observed with some agonists. These findings suggest that propranolol does not significantly affect platelet function when taken at doses commonly encountered in clinical practice. Beta blockers reduce the risk of mortality after myocardial infarction,'2 but the underlying reasons for this are unknown. Platelets play a part in the pathogenesis of coronary events,3 and the attendant hyperreactivity of platelets can be normalised by the use of propranolol.4 In vitro and in vivo studies of the action of f blockers on platelets, however, have yielded conflicting results,"'0 which can be partly explained by differences in dose and the ancillary properties ofthe drugs studied. Theoretical considera-tion of platelet adrenoreceptors indicates that non-selective f blockers such as propranolol may enhance aggregatory responses,'0 potentially undesirable in myocardial infarction. Platelet aggregation and other measurements of platelet activation are unaffected by the selective f blocker metoprolol. " We undertook a study to determine whether a therapeutic dose of propranolol would affect standard tests of platelet function in a group of healthy young subjects. Subjects and methods Seventeen healthy volunteers aged 18 to 37 years took part. Informed consent was obtained in each case and approval was obtained from the hospital ethical committee. No substances with antiplatelet activity in the 10 days preceding or during the study period were allowed. On each occasion blood was taken from an antecubital vein without stasis using a 21G butterfl