Precursor to metabolite: Methsuximide to N-desmethylmethsuximide

Methsuximide is converted to N-desmethylmethsuximide by hepatic demethylation.

The pair

Methsuximide — Succinimide for refractory absence seizures; the active metabolite does the work.
N-desmethylmethsuximide — Active metabolite of methsuximide; the long half-life that does the work.