N-acetylprocainamide is the major active metabolite of which drug?

N-acetylprocainamide is the major active metabolite of which drug?

• A. Phenobarbital
• B. Quinidine
• C. Lidocaine
• D. Procainamide

Answer: (D)

N-acetylprocainamide is formed when procainamide is N-acetylated in the liver, and this metabolite provides much of the drug’s sustained antiarrhythmic effect. Because NAPA is the major circulating metabolite, its activity and pharmacokinetics significantly influence the overall efficacy and safety of therapy. NAPA is cleared by the kidneys, so renal function and acetylator status (slow vs fast acetylators) affect its levels; this can lead to accumulation and increased risk of adverse effects if dosing isn’t adjusted. The other drugs listed do not produce N-acetylprocainamide as their major metabolite, so this metabolite is specific to procainamide’s metabolic pathway.

N-acetylprocainamide is formed when procainamide is N-acetylated in the liver, and this metabolite provides much of the drug’s sustained antiarrhythmic effect. Because NAPA is the major circulating metabolite, its activity and pharmacokinetics significantly influence the overall efficacy and safety of therapy. NAPA is cleared by the kidneys, so renal function and acetylator status (slow vs fast acetylators) affect its levels; this can lead to accumulation and increased risk of adverse effects if dosing isn’t adjusted. The other drugs listed do not produce N-acetylprocainamide as their major metabolite, so this metabolite is specific to procainamide’s metabolic pathway.