The free fraction of valproic acid in tears, saliva, and cerebrospinal fluid.

Valproic acid (VPA) was determined by EMIT assay in plasma, tears, saliva, and cerebrospinal fluid (CSF) of patients with epilepsy. Closer correlation was shown between tear/plasma and tear/CSF ratios than between saliva/plasma and saliva/CSF ratios. The VPA CSF/serum ratio was in good agreement with data in the literature. Salivary levels were extremely erratic, while those for tears were much more reliable. Determination of VPA in tears is therefore the best method of studying the VPA free fraction in those cases in which investigations of protein binding of the drug are necessary.