Valproic acid in breast milk: how much is really there?

Valproic acid (VPA) concentrations were measured by a sensitive and highly specific gas chromatographic/mass spectrometric assay in breast milk from 16 patients treated with VPA during 17 lactation periods. The range of VPA levels in 36 breast milk samples was 0.4-3.9 micrograms/ml (mean 1.9 +/- 1.2 microgram/ml). During the investigations of breast milk it was found that the concentration of total VPA in breast milk was not much higher than that of unbound VPA. These findings agree with clinical observations of infants fed with milk from VPA-treated mothers.