Gas-chromatographic determination of levamisole in human plasma-normalization and reliability of the method

Levamisole has been used by many authors as an immunostimulant agent but the relationship between oral doses, plasma level and the therapeutic effects were not known. For such a study it was necessary to establish an accurate and reproducible method of measurement. We describe a modification of the gas chromatographic method of Wynants et al. (1975). The normalization of the extraction of the extraction process leads to greater reliability and accuracy (4 ng +/- 7.6%). Reproducibility was established using a series of 30 determinations from standard solutions and plasmas supplemented with Levamisole. The relative standard deviation in K evaluation was varied between 0.9 and 1.8%, 3.7 and 6.1% for standard solutions and plasmas respectively. Consequently this method was adopted for this pharmacokinetic study which was carried out on healthy and cancer patients.