Time-course changes in lamotrigine concentration after addition of valproate and the safety and long-term tolerability of lamotrigine-valproate combination therapy

Biol Pharm Bull. 2023 Nov 10. doi: 10.1248/bpb.b23-00608. Online ahead of print.ABSTRACTThe aim of this study was to evaluate the time-course changes in lamotrigine (LTG) concentration after addition of valproate (VPA) and the safety and tolerability of the combination therapy.We reviewed our therapeutic drug monitoring (TDM) database and found 345 patients on LTG who received add-on therapy with VPA. VPA had been added at least 12 weeks after patients finished stepwise LTG titration. Also, we retrospectively evaluated the LTG concentration after addition of VPA and the safety and long-term tolerability of LTG-VPA combination therapy.Plasma LTG concentration increased more than 1.5-fold within 15 days of addition of VPA and reached a peak at 30 days. The rate of increase in LTG concentration occurred in a VPA concentration-dependent manner. During the first 120 days after addition of VPA, adverse events were reported by 58 patients (16.8%), but no patient developed cutaneous reactions. Kaplan-Meier analysis showed estimated retention rates for LTG-VPA combination therapy of 74.5% at 5 years. At 5 years, the mean concentration of LTG was 11.1 μg/mL (43.3 μmol/L).Because addition of VPA leads to a marked increase in LTG concentration over a short period, TDM for LTG should be performed at the earliest from 14 days after starting VPA. At 120 days after starting VPA therapy, the higher LTG concentration due to addition of VPA is not associated with an increased risk of cutaneou...
Source: Biological and Pharmaceutical Bulletin - Category: Drugs & Pharmacology Authors: Source Type: research