Precursor to metabolite: Carbamazepine ER capsules to Carbamazepine-10,11-epoxide

Carbamazepine ER capsules is converted to Carbamazepine-10,11-epoxide by CYP3A4.

The pair

Carbamazepine ER capsules — Bead-filled extended-release carbamazepine capsule that can be opened and sprinkled.
Carbamazepine-10,11-epoxide — Active epoxide metabolite of carbamazepine; cleared by epoxide hydrolase, which valproate inhibits.

Anything that inhibits or induces CYP3A4 shifts the balance between Carbamazepine ER capsules and Carbamazepine-10,11-epoxide.