Precursor to metabolite: Diazepam to Nordiazepam

Diazepam is converted to Nordiazepam by CYP2C19.

The pair

Diazepam — Rapid-onset, long-acting benzodiazepine for seizures, alcohol withdrawal, and muscle spasm.
Nordiazepam — Long-acting active metabolite of diazepam and several other benzodiazepines; accumulation can prolong sedation.

Anything that inhibits or induces CYP2C19 shifts the balance between Diazepam and Nordiazepam.