LACK OF INTERACTION OF GABAPENTIN WITH CARBAMAZEPINE OR VALPROATE

Gabapentin (GBP) studies were conducted in patients with epilepsy rece iving carbamazepine (CBZ, n = 12) or valproate (VPA, n = 14) monothera py. The effects of GBP coadministration on steady-state CBZ or VPA con centrations and of these antiepileptic drugs (AEDs) on GBP pharmacokin etics were investigated. GBP (400 mg) was coadministered every 8 h for 31/3 days with CBZ or for 51/3 days with VPA. GBP was well tolerated. Mean steady-state plasma CBZ/CBZ-10,11-epoxide (CBZ-E) and serum VPA concentrations before, during, and after GBP administration were not s ignificantly different. Mean steady-state GBP pharmacokinetic paramete rs during CBZ or VPA coadministration were similar to steady-state par ameters reported in healthy subjects. Thus, no pharmacokinetic interac tion exists between CBZ or VPA and GBP. No dosage adjustment is necess ary when GBP and CBZ or VPA are coadministered.