Effect of timolol on platelet aggregation in coronary heart disease.
The immediate effect of beta-blockers versus placebo in platelet function was studied in ten healthy men one hour after either 40 mg propranolol, 5 mg timolol or placebo was given. Both beta-blockers had similar platelet effects. They increased the ADP-threshold in a platelet aggregation test and reduced the plasma level of beta-thromboglobulin whereas the primary aggregation remained unchanged. Forty-four patients were given timolol 10 mg twice daily or corresponding placebo medication in a secondary prevention trial after a myocardial infarction. At rest and also immediately after a near maximal exercise test the platelet function was similar on timolol and placebo. During exercise a lower ADP-threshold and a higher plasma level of beta-thromboglobulin was observed irrespective of whether the patients received placebo or timolol. Thus, the acute platelet inhibiting effect of timolol observed after a single dose disappeared during chronic timolol treatment. During 24 hours continuous ambulatory ECG monitoring patients on timolol treatment had significantly less arrhythmias than patients on placebo. A general effect on platelets cannot explain this antiarrhythmic effect of timolol during chronic therapy.
D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects; D002986:Clinical Trials as Topic; D003327:Coronary Disease / Q000097:blood* / Q000503:physiopathology; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood; D005082:Physical Exertion; D010974:Platelet Aggregation / Q000187:drug effects*; D011412:Propanolamines / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D013999:Timolol / Q000494:pharmacology*
D011412:Propanolamines; D013999:Timolol; D011433:Propranolol