Valproic acid treatment is associated with altered leukocyte subset development.

Valproic acid (VPA) has been used for decades in the treatment of epilepsy and psychiatric disorders, and the long-term use of VPA is regularly accompanied by hematological toxicity, including neutropenia. More recently, it has been demonstrated that VPA can be used as a histone deacetylase inhibitor (HDACi) for the treatment of hematological malignancies. In order to determine the specific effects of VPA in both hematological malignancies and normal hematopoiesis, recent studies have demonstrated that VPA treatment affects the differentiation of normal myeloid progenitors in vitro. In this study, we demonstrate that in a large patient population treated for neurological or psychiatric disorders, VPA treatment affects neutrophil as well as lymphocyte subset counts.