Objective The study aimed to evaluate the impact of smoking on platelet inhibition of clopidogrel.

Methods The clopidogrel-native patients were enrolled. Cigarette smoking status was recorded and stratified into never smoking (NS) and current smoking (CS). All the patients were given loading dose of 300 mg and maintenance dose of 75 mg clopidogrel. Platelet aggregation was measured before and 24 h after loading by conventional light transmittance aggregometry after stimulation with 5 mmol/L ADP.

Results 722 patients (60.7±9.0 years) were enrolled, including 568 men (78.7%). Among the patients, 322 patients (44.6%) were CS and 400 (55.4%) were NS. At baseline, the maximal platelet aggregation (MPA) was not significantly different between CS and NS (57.2±10.4% and 56.6±12.8%, p=0.487). After clopidogrel loading, the MPA decreased significantly among CS compared with NS. The mean decreased MPA was 23.8±10.5% and 19.2±12.8% (p<0.001) for CS and NS, respectively.

Conclusion Cigarette smoking might enhance the inhibition effect of clopidogrel on platelet.