Lixivaptan and hyponatremia

A new selective, and sensitive method for the determination of lixivaptan, a vasopressin 2 (V2)-receptor antagonist, in mouse plasma and its application in a pharmacokinetic study

A new, selective and sensitive HPLC method for the determination of lixivaptan, an oral selective vasopressin 2 (V2)-receptor antagonist, was investigated and validated. A Waters symmetry C18 column was used as a stationary phase in isocratic elution mode using a mobile phase composed of KH2PO4(100 mM)-acetonitrile (40: 60, v/v) at a flow rate of 1.5 mL min-1. Diclofenac was used as the internal standard (IS). Lixivaptan and the IS were extracted from plasma by protein precipitation and were detected at 260 nm. Lixivaptan and diclofenac were eluted at 3.6 and 6.2 min, respectively. The developed method showed good linearity over the calibration range of 50 -1000 ng mL-1with a lower limit of detection of 16.5 ng mL-1. The extraction percentage of lixivaptan in the mouse plasma was in the range of 88.88 - 114.43%, which indicates acceptable extraction. The aforementioned method was validated according to guidelines of the International Council on Harmonization (ICH). The intra- and inter-day coefficients of variation did not exceed 5.5%. This method was presented to be simple, sensitive, and accurate and was successfully adapted in a pharmacokinetic study of the profile of lixivaptan in mouse plasma. A mean maximum plasma concentration of lixivaptan of 113.82 ng mL-1was achieved in 0.5 h after oral administration of a 10 mg kg-1dose in mouse as determined using the developed method.

Development and validation of HPLC-MS/MS method for the determination of lixivaptan in mouse plasma and its application in a pharmacokinetic study

The aim of the present study was to develop a simple, sensitive and accurate liquid chromatography-electrospray ionization tandem mass spectrometry (ESI-MS/MS) method for the determination of lixivaptan (LIX) in mouse plasma using vildagliptin as the internal standard (IS). A precipitation procedure was used for the extraction of LIX and vildagliptin from mouse plasma. Chromatographic separation of LIX was achieved using a C₁₈ analytical column (50 × 2.1 mm, 1.8 μm) at 25°C. The mobile phase comprised acetonitrile and ammonium formate (10 mm, pH 3.1; 40:60, v/v) pumped at a flow rate of 0.3 mL min^-1 . A tandem mass spectrometer with an electrospray ionization source was used to perform the assay. Quantification of LIX at m/z 290 → 137 and IS at 154 → 97 was attained through multiple reaction monitoring. The investigated method was authenticated following the bio-analytical method of validation guidelines of the US Food and Drug Administration. The developed method showed a good linearity over the concentration range from 5 to 500 ng mL^-1 , and the calibration curve was linear (r = 0.9998). The mean recovery of LIX from mouse plasma was 99.2 ± 0.68%. All validation parameters for LIX were within the levels required for acceptance. The proposed method was effectively used for a pharmacokinetic study of LIX in mouse plasma.