Pharmacokinetic comparison of seven 8-methoxypsoralen brands

The pharmacokinetics of seven 8-MOP brands were evaluated in 7 volunteers using an incomplete bloc design. After a single oral dose the 8-MOP plasma level was followed for 3 hours. The plasma concentration was measured with a gas chromatographic - mass spectrometric method, using an isotopic dilution technique. The different brands could be divided into three groups. Two gave a high maximum concentration, four a medium, and one a low concentration. The large interbrand variation observed in this study can explain the variations in the results of the treatment and the differing numbers of joules required to clear the patients in various PUVA centers.