Development of a Practical HPLC Method for In-hospital Quantitation of Various Medicinal Drugs at Blood Levels

Therapeutic drug monitoring (TDM) is very important in the clinical management of drug therapy based on the assessment of individual variability of the efficacy, side-effects, metabolism and genetic factors. However, it is hard to perform TDM in hospital routinely, because the blood level of each different drug is quantified by different analytical methods using various types of apparatus, devices and chemicals. In this study, a practical HPLC method was developed for the in-hospital quantitation of blood levels of various medicinal drugs, based on almost the same procedure. The method consists of a solid-phase extraction (SPE) of a drug in serum using a disposable centrifugal cartridge, and following conventional HPLC/UV analysis of a drug in a SPE eluate. At first, the conditions of the SPE treatment and HPLC analysis were optimized for each drug. Next, the SPE recovery % of drug from serum was determined for each drug. Finally, quantitation of the blood level of each drug was performed with our absolute calibration curve method corrected by each SPE recovery %. The present method is applicable to quantitation of blood levels of fifteen different medicines; the values of lower limit of quantification (LLOQ) were over a range of 0.10 - 1.48 mu g mL(-1). The method was also well-validated for each medicine in the range of its effective concentration. It will thus be a useful tool for the routine-implementation of TDM of the fifteen different medicines operated by a full-time staff in a hospital, such as a clinical laboratory technician and/or pharmacist.