Adding carbamazepine to valproic acid.
| || |
- Valproic acid is principally metabolized by CYP2C9, CYP2C19, CYP2A6 and UDP-glucuronosyltransferases. Valproic acid is an inhibitor of the enzymes CYP2C9, epoxide-hydroxylase and UDP-glucuronosyltransferases.
| || |
- Carbamazepine is principally metabolized by CYP3A4, and is a potent inducer of CYP1A2, CYP2C9, CYP3A4 and UDP-glucuronosyltransferases.
- A synergistic effect is suggested.
- Valproate can increase carbamazepine-epoxide serum concentrations. Define valproate serum concentration before starting carbamazepine.
- Start carbamazepine according to the general dosing advice. Check valproate and carbamazepine serum concentration (+ epoxide) after 2 weeks of therapy and adapt dose if necessary. 
- Valproate can inhibit carbamazepine metabolic pathways, resulting in raised carbamazepine-epoxide concentrations.  Valproate can also displace protein-bound carbamazepine and therefore increase the levels of free carbamazepine. This may result in neurotoxicity even when valproate levels are low.
- Carbamazepine induces metabolism of both itself and valproate via Cytochrome P450 3A3/4 system, which may decrease the serum concentrations of both drugs and increase the risk of relapse.
The editors of psychiatrienet.nl take the greatest care to provide up-to-date and accurate information on this site. Nevertheless, mistakes and omissions cannot be entirely excluded. No rights devolve from the information provided. The editors and other providers of information to this site accept no responsibility for the content of this site or for the information provided therein; neither do they accept responsibility for possible damages which may derive from the use of the information on this site or from the linked sites. The editorial board accepts no responsibility for the content of the (linked) sites, for access to them, or for the products and services on these sites, nor for the occurrence of errors, viruses, and/or disruptions in service.