Effects of dosage in new users of lamotrigine inducing epidermal necrolysis: Results of the German Registry of Severe Skin Reactions.

Objective: This study was undertaken to determine the impact of dosage in new users of lamotrigine (LTG) and the concomitant intake of valproic acid (VPA) on epidermal necrolysis (EN).

Methods: A total of 102 EN cases with exposure to LTG were identified (1992-2018) in the German Registry of Severe Skin Reactions. All cases are validated by an independent expert committee. Six cases were excluded due to lack of exposure in the relevant time frame. Causality assessment was performed with ALDEN (Algorithm for Assessment of Drug Causality in EN) on definite/probable cases (≥12 years; n = 84). Evaluation of dosing regimen was restricted to cases with complete LTG dosing history (n = 74).

Results: Demography showed a mean age of 42.4 years, female predominance (69%), and low mortality (7.3%). Epilepsy was the indication for use in 87.5%. LTG was the very probable cause in 71.4% and probable cause in 28.6%. On average, one additional antiseizure medication was taken, most frequently VPA (43/84). Combined LTG/VPA treatment showed no statistically significant difference in morbidity or mortality. Mean time latency from initiation of LTG to reaction onset was 24.2 days, varying between 21 days with high initial dose and 29.2 days with low initial dose. Low initial LTG dose (n = 9) revealed higher mortality (22.2%) and higher severity (5/9) than high initial dose (n = 35, mortality = 14.3%, 14/35 higher severity). No patient died when the starting dose was as recommended. The highest mortality (25%) was found in patients with no dose increase (n = 8), which correlated with higher age. Despite the recommended or low initial dose, 52.7% of patients developed EN, in contrast to 39.2% with a slow, recommended, or no dose escalation.

Significance: Neither the initial dose, dose escalation, nor the combination with VPA seems to influence the general occurrence of EN. However, EN patients with the recommended starting dose and the recommended dose escalation had the best outcome in terms of clinical severity and mortality.