Rash during lamotrigine treatment is not always drug hypersensitivity: A retrospective cohort study among children and adults.

Purpose Cutaneous adverse drug reactions (cADRs) are a major cause of lamotrigine (LTG) discontinuation. Remarkable variation in their reported incidence suggests confounders and diverse terms and definitions. The aim of this study was to identify immunological cADRs and to throw light on classification and differential diagnoses in children and adults. Methods Hospital records of 2683 patients with epilepsy (1897 adults, 786 children) were retrospectively screened. Of these, 403 patients (236 adults, 167 children) with first time exposure to LTG were reviewed. Skin reactions were categorized into possible or probable cADRs due to LTG hypersensitivity, and other skin reactions (OSRs) unlikely to be caused by this mechanism. Results 29 of 403 patients (7.2%) reported emergent skin symptoms within 3 months of treatment with LTG of which 20 (5%: 5.9% adults, 3.6% children) were categorized as possible or probable cADRs. Concomitant infection appeared to be present in several cases, particularly in children. OSRs were found in 4.2% of the children using LTG, compared to 0.8% of the adults (p = 0.04). Conclusions Rash during the early phase of LTG treatment is not always drug hypersensitivity. Whenever skin symptoms occur, other potential causes should receive attention to avoid needless discontinuation, particularly in children. However, when early symptoms and signs of severe cADRs are suspected, LTG should promptly be discontinued.