Plasma concentrations after bath treatment and oral administration of trioxsalen.

An analytical method comprising homogenous extraction and determination by gas chromatography mass spectrometry has been developed for the quantitation of trioxsalen in plasma. The limit of sensitivity of the method has been 2 ng/ml of trioxsalen. The method was used to monitor concentrations of trioxsalen in plasma after a 40 mg oral dose or after trioxsalen bath treatment. The concentrations in plasma after oral administration did not exceed 3 ng/ml, while in 2 patients after bath treatment trioxsalen could be determined (2-3 ng/ml). The low plasma concentrations found throw light on the poor UV-sensitizing properties found after oral trioxsalen therapy.