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Smoking Enhances Platelet Inhibition By Plavix

May explain some variability in patient response

TUESDAY, Aug. 5 (HealthDay News) -- Cigarette smoking enhances platelet inhibition by clopidogrel (Plavix), which may explain some variability in patient response to the drug, according to a report in the Aug. 12 issue of the Journal of the American College of Cardiology.

Kevin P. Bliden, from the Sinai Center for Thrombosis Research in Baltimore, and colleagues examined whether cigarette smoking affected the platelet response to clopidogrel in 259 patients undergoing elective coronary stenting. Of these, 120 were on chronic clopidogrel treatment, 139 had not previously received clopidogrel and were treated with 600 mg of the drug, 104 were current smokers and 155 were non-smokers. Smoking induces the CYP1A2 liver enzyme, which also activates clopidogrel, they note.

The researchers found that smokers on either chronic clopidogrel treatment or newly receiving the drug had significantly lower adenosine diphosphate (ADP)-stimulated platelet aggregation and ADP-stimulated active glycoprotein IIb/IIIa expression compared with non-smokers. Current smoking was a significant independent predictor of low platelet aggregation.

"Clopidogrel therapy in current smokers is associated with increased platelet inhibition and lower aggregation as compared with non-smokers," Bliden and colleagues conclude. "The mechanism of the smoking effect deserves further study and may be an important cause of response variability to clopidogrel therapy."

The study was funded by Daiichi Sankyo and Sinai Hospital of Baltimore.

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