An LC-MS/MS-ESI method for the quantification of betamethasone in bioequivalence studies

A simple, sensitive, and rapid liquid chromatography-mass detection (LC-MS/MS) method for the analysis of betamethasone (BET) from intramuscular injection of phosphate and dipropionate BET produgs was developed for bioequivalence studies in human plasma. The calibration curve was linear over the range of concentrations (0.5–50.0 ng mL-1; r2 = 0.99), showing a very high sensitivity without interferences at the retention times of BET (0.8 min) and the internal standard (IS) triamcinolone acetonide (0.95 min). Both drug (D) and IS were extracted from human plasma by liquid-liquid extraction, showing average recovery values of 94.0 and 98.9%, respectively. Within- and between-run precision studies demonstrated a variation coefficient <10% at all tested concentrations. Therefore, our analytical method proved to be validated according to the worldwide-accepted FDA guidelines and successfully applied for bioequivalence studies of parenteral formulations containing BET dipropionate (5 mg mL−1) and BET sodium phosphate (2 mg mL-1).