What is the major active metabolite of the anticonvulsant drug primidone?

What is the major active metabolite of the anticonvulsant drug primidone?

• A. Phenytoin
• B. Acetazolamide
• C. NAPA
• D. Phenobarbital

Answer: (D)

Primidone acts as a prodrug for its anticonvulsant activity. In the liver, it is metabolized to two active products, with phenobarbital providing the majority of the therapeutic effect. Phenobarbital is a potent GABA_A receptor agonist that enhances inhibitory neurotransmission, giving a long-lasting antiseizure effect. While the other metabolite (and other anticonvulsants listed) may contribute to activity in some contexts, they do not account for the main anticonvulsant action of primidone. Phenytoin and acetazolamide are not formed from primidone, and while NAPA can be a metabolite, it is not the primary contributor to the drug’s major clinical effect.

Primidone acts as a prodrug for its anticonvulsant activity. In the liver, it is metabolized to two active products, with phenobarbital providing the majority of the therapeutic effect. Phenobarbital is a potent GABA_A receptor agonist that enhances inhibitory neurotransmission, giving a long-lasting antiseizure effect. While the other metabolite (and other anticonvulsants listed) may contribute to activity in some contexts, they do not account for the main anticonvulsant action of primidone. Phenytoin and acetazolamide are not formed from primidone, and while NAPA can be a metabolite, it is not the primary contributor to the drug’s major clinical effect.