Incidence of Neutropenia with Valproate and Quetiapine Combination Treatment in Subjects with Acquired Brain Injuries

Objective To investigate whether the incidence of neutropenia was higher in subjects who received a combination treatment with valproate and quetiapine than in those who were administered monotherapy. Design Retrospective cohort study. Setting Rehabilitation department of a university hospital. Participants Patients with acquired brain injuries who had taken valproate for seizures or quetiapine for delirium for >7 days (N=101). Data were extracted from electronic medical records of the hospital. Interventions Not applicable. Main Outcome Measures Incidence of neutropenia (absolute neutrophil count<2000 cells/μL) was elicited from the weekly complete blood cell records for 71.07±43.71 days of observation. The odds ratio for neutropenia development was calculated and adjusted for variables that showed significant differences between patients with or without neutropenia. Results The incidence of neutropenia was significantly higher in the group receiving the combination treatment than in those receiving the monotherapy (32.26% vs 12.90%, adjusted P=.036), despite a lack of any differences in the daily doses of the medications. Coadministration of quetiapine and valproate was the predictor of neutropenia development when age, body weight, and underlying diseases were adjusted in the logistic regression model (odds ratio=3.749; 95% confidence interval, 1.161-12.099; P=.027). Conclusions Administration of quetiapine together with valproate in patients with acquired brain injury could increase the incidence of medication-induced neutropenia.