ObjectiveTo investigate the effect of valproic acid (VPA) coadministred with lamotrigine (LTG) on epileptic patients' ammonia and evaluate the influencing factors of elevated blood ammonia in epileptic patients.MethodsA retrospective analysis of clinical data from 146 patients with epilepsy (including newly diagnosed epilepsy patients) who were admitted to the Seventh Affiliated Hospital of Sun Yat-Sen University from May 2018 to April 2020 was performed. The patients were divided into no antiepileptic drug group (group A), VPA group only (group B) and VPA combined LTG group (group C), and the concentration of the blood ammonia of the patients were analyzed.ResultThe average ammonia levels in groups A, B and C were (18.14±1.19), (25.89±0.87) and (36.60±4.34) μmol/L, and the incidence of blood ammonia higher than normal were 2.77%, 8.89% and 20.0%, respectively.The difference between group B and group A and group C were statistically significant (P<0.05), the difference between group C and group A was statistically significant (P<0.05).ConclusionPatients with epilepsy who use VPA were at increased risk of blood ammonia and LTG can increase ammonia in epileptic patients who were treated with VPA. So when VPA was combined with LTG, more attention should be paid to ammonia of patient to avoid adverse reactions.