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.

Development of highly selective and sensitive molecularly imprinted polymer-based electrochemical sensors for tolvaptan assay in tablets and serum

In this research, two different molecularly imprinted polymer (MIP)-based electrochemical sensors were proposed for the determination of tolvaptan (TOL). Photopolymerization (PP) and thermal polymerization (TP) techniques were developed for the determination of TOL. The advantages of MIP were used to design an electrochemical sensor for selective and sensitive determination of TOL. TOL was determined on a glassy carbon electrode (GCE) using differential pulse voltammetry (DPV) for both techniques. Some important parameters affecting the sensor efficiency, such as template/monomer ratio, PP and TP time, drop volume, removal solutions, removal and rebinding time, etc., were optimized. The surface characterization of the proposed MIP-based electrochemical sensors was carried out with electrochemical characterization by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. It was extended with the scanning electron microscopy (SEM) technique. Under optimal conditions, the developed sensors showed good linearity between 1.0 × 10-11 M and 1.0 × 10-10 M, and 2.5 × 10-11 M and 2.5 × 10-10 M for PP and TP, respectively. Low detection limits (2.89 × 10-12 M (PP) and 1.88 × 10-13 M (TP)) were also obtained for TOL determination. The applicability of the proposed sensor was evaluated using tablet and commercial human serum samples. Interference and imprinting factor studies verified the selectivity and specificity of the proposed sensors, and the efficiency of the sensors was verified using an unprinted polymer for comparison at each step.

Diuretics in Different Samples: Update on the Pretreatment and Analysis Techniques

Diuretics are drugs that promote the excretion of water and electrolytes in the body and produce diuretic effects. Clinically, they are often used in the treatment of edema caused by various reasons and hypertension. In sports, diuretics are banned by the World Anti-Doping Agency (WADA). Therefore, in order to monitor blood drug concentration, identify drug quality and maintain the fairness of sports competition, accurate, rapid, highly selective and sensitive detection methods are essential. This review provides a comprehensive summary of the pretreatment and detection of diuretics in various samples since 2015. Commonly used techniques to extract diuretics include liquid-liquid extraction, liquid-phase microextraction, solid-phase extraction, solid-phase microextraction, among others. Determination methods include methods based on liquid chromatography, fluorescent spectroscopy, electrochemical sensor method, capillary electrophoresis and so on. The advantages and disadvantages of various pretreatment and analytical techniques are elaborated. In addition, future development prospects of these techniques are discussed.

Simple Liquid Chromatography-Tandem Mass Spectrometry Method for Quantitation of Total and Free Aprepitant and Its Active N-Dealkylated Metabolites in Human Plasma

BACKGROUND

Aprepitant, an antiemetic selective neurokinin-1 receptor antagonist, is primarily metabolized to the active N-dealkylated form (ND-AP) and then converted to its carbonyl form (ND-CAP) in humans. This study developed a simple liquid chromatography-tandem mass spectrometry method using electrospray ionization for the quantitation of plasma total and free aprepitant and its N-dealkylated metabolites and used them to analyze patient plasma.

METHODS

Free aprepitant and ND-AP in plasma were fractionated using centrifugal ultrafiltration. The analytes in plasma or their ultrafiltered specimens treated with triethylamine/acetonitrile were isocratically separated using a 3-μm octadecylsilyl column with a total run time of 10 minutes and scanned using positive ion electrospray ionization.

RESULTS

The calibration curves of total aprepitant, ND-AP, and ND-CAP were prepared at concentration ranges of 50-2500, 20-1000, and 5-250 ng/mL, respectively, whereas that of free aprepitant and ND-AP were at a concentration range of 2-150 ng/mL. The intraassay and interassay accuracy and imprecision values were 93.5%-107.7% and 94.6%-103.3%, and 2.1%-7.5% and 1.0%-8.9%, respectively. Aprepitant and its metabolites did not exhibit any matrix effects or instabilities in the plasma specimens. In cancer patients receiving oral aprepitant, the plasma concentration ranges of total aprepitant, ND-AP, and ND-CAP, and free aprepitant and ND-AP were 137-2170, 104-928, 22.4-97.6, 8.11-60.0, and 3.53-56.0 ng/mL, respectively. The median plasma free fraction proportion of aprepitant and ND-AP was 4.14% and 4.90%, respectively.

CONCLUSIONS

The present developed method showed an acceptable analytical performance and can be used to evaluate total and free aprepitant and its N-dealkylated metabolites in patient plasma.

An enantiomeric quantitative LC-MS/MS method for tolvaptan and its monohydroxylates in human plasma using a reversed-phase separation procedure

Racemic tolvaptan possessing an asymmetric carbon is metabolized to three pairs of monohydroxylate enantiomers of diol form with V₂ receptor antagonistic activity via CYP3A. This study aimed to develop a simultaneous quantitative liquid chromatography-tandem mass spectrometry method for 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in human plasma and to apply it to patient samples. Deproteinized plasma specimens were separated using a polysaccharide derivative chiral column in a reversed-phase elution mode. The mass spectrometer was run in positive ion electrospray ionization mode. The chromatographic peaks of tolvaptan monohydroxylate enantiomers were identified by the recombinant CYP3A4/5 digestion of 5R- and 5S-tolvaptan. The calibration curves ranged over the plasma concentrations of 0.25-125 ng/mL for 5R- and 5S-tolvaptan, 0.025-12.5 ng/mL for 4R5R- and 4S5S-diols, and 0.025-38.15 ng/mL for 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols with a large variation. Their pre-treatment recovery rates and matrix factors in human plasma were 85.2-112.9 % and 86.9-113.1 %, respectively. The intra- and inter-day accuracy and imprecision were 92.3-113.8 % and 3.5-14.6 % for all analytes, respectively. The plasma concentration ranges of 5R- and 5S-tolvaptan, 4R5R-, 4S5S-, 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols in heart failure patients with a 5-fold dilution procedure were 0.634-28.4, 2.37-131, 0.525-15.4, 0.0970-4.08, 6.82-108, 0.271-6.49, 0.394-4.18, and 4.81-39.8 ng/mL, respectively. In conclusion, the present method has an acceptable analytical performance level and can be helpful for characterization of the plasma 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in heart failure patients.