Evaluation of a miniature mass spectrometer based point-of-care-test method for direct analysis of amlodipine and benazepril in whole blood.

A miniature mass spectrometer (mMS) based point-of-care testing (POCT) method was evaluated for on-site detecting the hypertension drugs, amlodipine and benazepril. The instrument parameters, including voltage, ISO1, ISO2, and CID, were optimized, under which the target compounds could be well detected in MS2. When these two drugs were injected simultaneously, the mutual ionization inhibition and mutual reduction between amlodipine and benazepril were evaluated. This phenomenon was severe on the precursor ions but had a small impact on the product ions, thus making this POCT method suitable for analysis using product ions. Finally, the method was validated and applied. The blood samples from patients were tested one hour after oral administration of the drugs (20 mg), and the benazepril was quantitatively analyzed using a standard curve, with detected concentrations ranging from 190.6 to 210 µg L-1 and a relative standard deviation (RSD) of 8.6 %. In summary, amlodipine has low sensitivity and can only be detected at higher concentrations, while benazepril has high sensitivity, good linearity, and even meets semi-quantitative requirements. The research results of this study are of great clinical significance for monitoring blood drug concentrations during hypertension medication, predicting drug efficacy, and customizing individualized medication plans.

Development, validation and application of a UPLC-MS/MS method for simultaneous quantification of OPC-61815 and its metabolites tolvaptan, DM-4103 and DM-4107 in human plasma.

OPC-61815 is an intravenous formulation vasopressin antagonist designed to treat heart failure patients, especially who have difficulty in oral intake. Tolvaptan together with DM-4103 and DM-4107 are considered as the major metabolites of OPC-61815 biotransformed in the liver via cytochrome P450 (CYP) 3A. An efficient and robust ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for quantification of OPC-61815 and its three metabolites in human plasma was developed and fully validated. To our best knowledge, it was the first published method that simultaneously quantified all of these four analytes in only one run. Simple and rapid sample preparation procedure and very short UPLC-MS/MS run time (3.5 min) offered OPC-61815 and its metabolites relatively high throughput detection, which was greatly beneficial to further clinical bio-sample analysis. The method showed good linearity and sufficient sensitivity in the range of 2.00-1000 ng/mL with a low limit of quantitation (2.00 ng/mL) for each analyte. For samples with concentrations above 1000 ng/mL, 100-fold dilution with blank plasma before sample preparation was accepted. High precision and accuracy, high selectivity and satisfactory recovery of this method were demonstrated. For all of the four analytes, no significant matrix effect or carry-over was observed. The stability of analytes and internal standards under different conditions were evaluated to ensure they were stable during the whole period of storage, preparation and detection. Also, re-injection reproducibility was investigated. In addition, the conversion test showed that almost no OPC-61815 converted into DM-4103 and DM-4107 during sample processing, while attention should be paid to the concentration difference between OPC-61815 and tolvaptan in bioanalysis. The developed UPLC-MS/MS method was successfully applied to an open, single and multiple dose administration phase I trial for monitoring the pharmacokinetics of OPC-61815. This work provided a promising way for further pharmacokinetic study of OPC-61815.