A synthetic derivative of propylpentanoic acid with antiepileptic properties and potential antineoplastic and antiangiogenesis activities. In epilepsy, valproic acid appears to act by increasing the concentration of gamma-aminobutyric acid (GABA) in the brain. This agent's antitumor and antiangiogenesis activities may be related to the inhibition of histone deacetylases and nitric oxide synthase, which results in the inhibition of nitric oxide synthesis. or A drug used to treat epileptic seizures and bipolar disorder and to prevent migraine headaches. It is also being studied in the treatment of several types of cancer. It blocks an enzyme that cells need to grow and may cause cancer cells to die. It also blocks the growth of new blood vessels that tumors need to grow. It is a type of anticonvulsant, histone deacetylase (HDAC) inhibitor, antimaniacal, migraine headache prophylactic, and antiangiogenesis agent. Also called Depakene and Stavzor.