Second-Line Medications for Women Aged 10 to 50 Years With Idiopathic Generalized Epilepsy

Importance Women with idiopathic generalized epilepsy (IGE) face challenges in treatment due to limited options that are both effective and safe. Objective To evaluate the effectiveness and safety of substitution monotherapy vs add-on therapy as second-line options for women who might become pregnant with IGE after failure of first-line antiseizure medications (ASMs) other than valproic acid. Design, Setting, and Participants Multicenter retrospective comparative effectiveness cohort study at 18 primary, secondary, and tertiary adult and children epilepsy centers across 4 countries, analyzing data from 1995 to 2023. Participants were women aged 10 to 50 years diagnosed with IGE who were prescribed a second line of ASM. Main Outcomes and Measures Treatment failure (TF), defined as the replacement or addition of a second ASM due to ineffectiveness, was compared between patients receiving ASM add-on or substitution monotherapy using inverse probability of treatment weighting (IPTW)–adjusted Cox proportional hazards regression. Exploratory analyses were also conducted to assess the effectiveness of individual ASMs and various ASM combinations. Results This study included 249 women with a median (IQR) age of 18.0 (15.5-22.0) years. Among them, 146 (58.6%) received an add-on regimen, and 103 (41.4%) received substitution monotherapy. During follow-up, TF occurred in 48 patients (32.9%) receiving add-on therapy and 36 (35.0%) using substitution monotherapy, with no significant differences between groups (IPTW-adjusted hazard ratio [HR], 0.89; 95% CI, 0.53-1.51; P = .69). ASM discontinuation due to ineffectiveness or adverse effects occurred in 36 patients (24.7%) receiving add-on therapy and 29 (28.2%) receiving substitution monotherapy, showing no significant differences (IPTW-adjusted HR, 0.97; 95% CI, 0.57-1.65; P = .92). Rates of ASM discontinuation due to adverse effects only were low in both groups, occurring in 13 patients (9.0%) receiving add-on therapy and 9 (8.7%) receiving a substitution monotherapy. Among add-on regimens other than valproic acid, the combination of levetiracetam and lamotrigine demonstrated a lower risk of TF compared with other combinations with levetiracetam plus other ASM (adjusted HR, 2.41; 95% CI, 1.12-5.17; P = .02) and lamotrigine plus other ASM (adjusted HR, 4.03; 95% CI, 1.73-9.39; P = .001). However, valproic acid remained the most effective second-line ASM when considering individual agents. Conclusions and relevance In this comparative effectiveness study of second-line treatment strategies for women with IGE, no significant differences were observed between substitution monotherapy and add-on therapy.