What is the estimated half-life of Plavix?

• A. Six Hours
• B. Twelve Hours
• C. Twenty-Four Hours
• D. Forty-Eight Hours

Answer: (A)

Half-life is how long it takes for the drug level in the blood to drop by half. For clopidogrel (Plavix), the plasma half-life is about six hours. It’s a prodrug that is activated in the liver to metabolites that irreversibly inhibit the P2Y12 receptor on platelets. Because this binding is irreversible, the antiplatelet effect lasts well beyond the drug’s presence in the blood, persisting for the life of the platelets (roughly 7–10 days) until new platelets are made. So the expected half-life is around six hours, while the clinical effect remains longer due to the irreversible receptor blockade. The longer time options don’t match the typical pharmacokinetic data for clopidogrel.