Determination of benzonatate and its metabolite in human plasma by HPLC–MS/MS: A preliminary pharmacokinetic study in healthy Chinese volunteers after oral administration of benzonatate soft capsule

In this study, two sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS) methods were developed and fully validated for the determination of the original 4-(butylamino)benzoic acid (method B) and total 4-(butylamino)benzoic acid (containing the original 4-(butylamino)benzoic acid and 4-(butylamino)benzoic acid converted from benzonatate after collection, method A). For both methods, one-step protein precipitation by methanol was performed to extract analytes from the plasma samples. Chromatographic separation was done on an InfinityLab Poroshell 120 Phenyl Hexyl column (2.1 mm × 50 mm, 2.7 μm, Agilent) with initial mobile phase consisting of 5 mM ammonium acetate containing 0.3% formic acid and acetonitrile (60:40, v/v) at a flow rate of 0.3 mL/min. Quantification was achieved by multiple reaction monitoring (MRM) in electron spray ionization (ESI) positive mode with the transitions of m/z 194.2→138.1 and 515.3→497.3 for 4-(butylamino)benzoic acid and telmisartan (the internal standard), respectively. The two methods exhibited good linearity over the concentration range of 10–10000 ng/mL. Both of the methods were successfully applied to the preliminary pharmacokinetic study in healthy Chinese volunteers after oral administration of benzonatate soft capsule at a single dose of 100 mg. The results showed that 4-(butylamino)benzoic acid and benzonatate were rapidly absorbed and reached a maximum concentration (Cmax) of...
Source: Journal of Pharmaceutical and Biomedical Analysis - Category: Drugs & Pharmacology Source Type: research