Lamotrigine-Valproate Interaction: Relationship to the Dose of Valproate
Abstract number :
3.182
Submission category :
Year :
2000
Submission ID :
3323
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
John Decerce, Jeanee S McJilton, Mangala A Nadkarni, R. Eugene Ramsay, Seton Hall Univ Sch of Graduate Medical Education, Edison, NJ; Univ of Miami Sch of Medicine - Int'l Ctr for Epilepsy, Miami, FL.
RATIONALE: The addition or removal of valproate (VPA) to the regimen of patients maintained on lamotrigine (LTG) can have a significant impact on the apparent clearance (CL/F) of LTG. Neither the minimum dose of VPA required to affect LTG disposition, nor the dose above which little or no further effect occurs is known. METHODS: This is a prospective study in epileptic outpatients stabilized on LTG. Patients underwent either a slow step-wise introduction, or withdrawal of VPA. All patients followed the same dosing paradigm. The dose of LTG was kept constant throughout the study. Morning trough levels (Ctrough) of VPA and LTG were obtained every 3 weeks. RESULTS: LTG CL/F remained stable above VPA Ctrough of 14 ug/ml (see fig.). Daily VPA dosages above 250 mg had little impact on LTG Ctrough (table A, n=2). CONCLUSIONS: When adding VPA to LTG, the greatest impact on the plasma level of LTG occurs at dosage introduction. Similiarly, when VPA is withdrawn, LTG concentrations remain stable until the very end of a step-wise taper. Closer monitoring is advisable during these periods. ?Partially funded by GlaxoWellcome??