Habitual smoking causes an abnormality in platelet thromboxane A2 metabolism and results in an altered susceptibility to aspirin effects

The present study investigates the effects of aspirin (100 mg every second day for 14 days) on platelet function in nine healthy non-smokers and in nine healthy habitual smokers, There was a significantly (P<0.05) stronger inhibition of collagen (0.61 mu g/ml)- and ADP (2 mu M)-induced platelet aggregation by aspirin in smokers as compared to non-smokers. This difference occurred in the presence of an almost complete (>95%) inhibition of thromboxane A(2) (TXA(2)) synthesis in both groups, The platelet capacity to generate TXA(2) in vitro was significantly reduced in smokers, urinary excretion of TXA(2), however, was significantly increased. Thus, the better susceptibility of smokers to anti-aggregatory effects of aspirin is very likely to be related to a chronic smoking-induced alteration of platelet TXA(2) system. Cessation of smoking should, therefore, be encouraged.