Phenobarbital monotherapy for convulsive seizures in rural Northwest China: a 12-year longitudinal study

BACKGROUND: This study was conducted as part of the China Epilepsy Prevention and Control Management Project. The research aimed to investigate the efficacy of phenobarbital (PB) and prognostic factors for convulsive seizures in rural areas of northwest China. METHODS: Patients with convulsive seizures were recruited from seven rural regions in Shaanxi Province, Northwest China, between January 2011 and December 2022. Patients over 6 years old and had at least one convulsive seizure at baseline (within 12 months prior to screening) were included. They were prescribed PB monotherapy according to a standardized protocol. During follow-up, the efficacy of PB was annually estimated by the reduction in seizure frequency. At the five-year follow-up, prognosis was assessed by the proportion of patients who achieved three consecutive seizure-free years. RESULTS: A total of 1001 patients (mean age 40.9 years, 56.8% male) were included. The median follow-up duration was 5 years (interquartile range [IQR], 3-8; maximum 12 years). The median baseline seizure frequency was 5 seizures (IQR 3-12) per year. The proportion of patients achieving a 50% reduction in seizure frequency was 62.1% (622/1001) in the first year and 93.0% (133/143) by the tenth year, respectively. In total, 528 individuals achieved 3-year remission (3YR), 473 participants did not achieve 3YR. Patients who achieved 3YR demonstrated significantly higher rates of seizure freedom within the initial 24-month treatment period compared to non-3YR patients (89% vs 37%, respectively, P < 0.001). Multivariate analysis revealed that patients with a baseline seizure frequency exceeding 10 seizures per year had a significantly higher risk of failure to achieve 3YR (OR 2.13, 95%CI 1.63-2.78, P < 0.001). Adverse effects of PB were mostly mild, with 490 patients (48.9%) recording adverse reactions one month after prescription and decreased to 238 patients (23.8%) at their last visit (median follow-up 4 [IQR 2-7] years). CONCLUSIONS: Our study demonstrated that convulsive seizures could be effectively controlled with PB monotherapy with mild adverse effects in rural areas in Northwest China. Early treatment response, particularly seizure freedom within the first two years, is a strong indicator of long-term remission. High baseline seizure frequency is an independent risk factor for poor prognosis.