What is the active metabolite of procainamide?

• A. N-acetyl procainamide (NAPA)
• B. N-desacetyl procainamide
• C. Acetyl-CoA
• D. Procainamide-epoxide

Answer: (A)

Procainamide is mainly activated in the body by hepatic N-acetylation to form N-acetyl procainamide, known as NAPA. This metabolite retains antiarrhythmic activity, contributing to the overall effect of the drug. The amount of NAPA formed depends on individual genetics of the N-acetyltransferase enzyme (NAT2), so people can be fast or slow acetylators, which influences drug levels and potential toxicity.

The other options don’t represent the primary active metabolite: N-desacetyl procainamide is not the major product; acetyl-CoA is just a cellular acetyl donor and not a drug metabolite in this context; procainamide-epoxide is not the main clinically relevant metabolite.