The process involved in the biotransformation of amitriptyline to nortriptyline

The process involved in the biotransformation of amitriptyline to nortriptyline

• A. Ketone reduction
• B. Epoxidation
• C. Aromatic hydroxylation
• D. N-demethylation

Answer: (D)

N-demethylation is the metabolic step at work here. Amitriptyline has a tertiary amine with two methyl groups attached to nitrogen. In the body, liver enzymes—mainly cytochrome P450—remove one of those methyl groups, converting the tertiary amine into a secondary amine and producing nortriptyline. This transformation is a classic example of how drug molecules are biotransformed to more polar forms for easier elimination, while still often retaining pharmacological activity in the metabolite. The other processes described—ketone reduction, epoxidation, or aromatic hydroxylation—don’t reflect the specific change from amitriptyline to nortriptyline, which is defined by losing one methyl group from the nitrogen.

N-demethylation is the metabolic step at work here. Amitriptyline has a tertiary amine with two methyl groups attached to nitrogen. In the body, liver enzymes—mainly cytochrome P450—remove one of those methyl groups, converting the tertiary amine into a secondary amine and producing nortriptyline. This transformation is a classic example of how drug molecules are biotransformed to more polar forms for easier elimination, while still often retaining pharmacological activity in the metabolite. The other processes described—ketone reduction, epoxidation, or aromatic hydroxylation—don’t reflect the specific change from amitriptyline to nortriptyline, which is defined by losing one methyl group from the nitrogen.