Overview of therapeutic drug monitoring and clinical practice

With the rapid development of clinical pharmacy in China, therapeutic drug monitoring (TDM) has become an essential tool for guiding rational clinical drug use and is widely concerned. TDM is a tool that combines pharmacokinetic and pharmacodynamic knowledge to optimize personalized drug therapy, which can improve treatment outcomes, reduce drug-drug toxicity, and avoid the risk of developing drug resistance. To effectively implement TDM, accurate and sophisticated analytical methods are required. By researching the literature published in recent years, we summarize the types of commonly monitored drugs, therapeutic windows, and clinical assays and track the trends and hot spots of therapeutic drug monitoring. The purpose is to provide guidelines for clinical blood drug concentration monitoring, to implement individualized drug delivery programs better, to ensure the rational use of drugs for patients, and to provide a reference for the group to carry out related topics in the future.

Overview of therapeutic drug monitoring of immunosuppressive drugs: Analytical and clinical practices

Immunosuppressant drugs (ISDs) play a key role in short-term patient survival together with very low acute allograft rejection rates in transplant recipients. Due to the narrow therapeutic index and large inter-patient pharmacokinetic variability of ISDs, therapeutic drug monitoring (TDM) is needed to dose adjustment for each patient (personalized medicine approach) to avoid treatment failure or side effects of the therapy. To achieve this, TDM needs to be done effectively. However, it would not be possible without the proper clinical practice and analytical tools. The purpose of this review is to provide a guide to establish reliable TDM, followed by a critical overview of the current analytical methods and clinical practices for the TDM of ISDs, and to discuss some of the main practical aspects of the TDM.

APPROACHES TO THE DEVELOPMENT OF BIOANALYTICAL METHODS FOR DETERMINATION OF UNSTABLE SUBSTANCES IN BIOLOGICAL FLUIDS

The approaches to bioanalytical method development for determination of substances which contain unstable functional groups in the structure are described. The oxidation and the hydrolysis are main causes of the decomposition of substances in biological fluids. Phenolic hydroxyls contain drugs were selected as examples of oxidable compounds, glucuronides of drugs were selected as examples of hydrolysable compounds. Determination of mycophenolic acid, which contains one phenolic hydroxyl and metabolized by formation of glucuronides, in plasma was performed using high performance liquid chromatography with mass-spectrometry and tandem mass-spectrometry detection. Methyldopa, which contains two phenolic hydroxyls, in stabilized plasma was assayed by high performance liquid chromatography – tandem mass-spectrometry in the range of 0.02–3.00 μg/ml. Concentrations of desmethyl mebeverine acid, which contains in the structure one phenolic hydroxyl and metabolized by formation of phenolic glucuronide, was measured simultaneously with mebeverine acid in the range of 10–2000 ng/ml. The influence of the ion source conversion of glucuronides on the quantitative determination of the substances was studied in the initial part of methods development. The next, selection of anticoagulants based on the study of short-term stability and freeze/thaw stability of the analytes and back conversion of their glucuronides was performed. The combination of anticoagulant K3EDTA and the antioxidant solution containing a mixture of ascorbic acid, sodium sulfite and sodium hydrogen carbonate in the concentrations of 5.0 %, 0.2 % and 2.4 %, respectively, was used to prevent degradation of methyldopa.

Determination of mycophenolic acid in human plasma by ultra performance liquid chromatography tandem mass spectrometry

A simple, sensitive and high throughput ultra performance liquid chromatography tandem mass spectrometry method has been developed for the determination of mycophenolic acid in human plasma. The method involved simple protein precipitation of MPA along with its deuterated analog as an internal standard (IS) from 50 µL of human plasma. The chromatographic analysis was done on Acquity UPLC C18 (100 mm×2.1 mm, 1.7 µm) column under isocratic conditions using acetonitrile and 10 mM ammonium formate, pH 3.00 (75:25, v/v) as the mobile phase. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for quantitation. In-source conversion of mycophenolic glucuronide metabolite to the parent drug was selectively controlled by suitable optimization of cone voltage, cone gas flow and desolvation temperature. The method was validated over a wide concentration range of 15-15000 ng/mL. The mean extraction recovery for the analyte and IS was >95%. Matrix effect expressed as matrix factors ranged from 0.97 to 1.02. The method was successfully applied to support a bioequivalence study of 500 mg mycophenolate mofetil tablet in 72 healthy subjects.