[Individual dosing in methadone substitution therapy. Determination of concentration with high performance liquid chromatography in comparison to immunoassay].

Individual Dosing in Methadone Maintenance Therapy/Plasma level determination by means of high performance liquid chromatography versus immunoassay. Measuring plasma methadone levels during maintenance therapy is a matter of discussion. Yet, there has been surprisingly little interest in integrating therapeutic drug monitoring into methadone maintenance programmes. The reasons for this are practical. To achieve optimal results during methadone maintenance therapy, a plasma level higher than 200 ng/ml is desired at all times during treatment. In the present study, a total number of 124 plasma samples were estimated twice: by means of HPLC and by means of fluorescence polarization immunoassay (Abbott TDx). The coefficient of correlation was 0.96416. We conclude that therapeutic drug monitoring should become routine in methadone treatment to achieve optimum results, especially in patients who complain of withdrawal symptoms and continue high-risk behaviour. The used immunoassay was found to be safe and inexpensive.