Rapid LC-MS/MS method for determination of drotaverine in a bioequivalence study

A liquid chromatography coupled with tandem mass spectrometry method for the quantification of the antispasmodic drug drotaverine in human plasma was developed and validated according to the current bioanalytical guidelines. The internal standard used was imipramine. The separation was performed on a Kinetex C18 50×3mm, 2.6μm column under isocratic conditions using a mobile phase of 65:35 (v/v) formic acid 0.2% (v/v) in water and acetonitrile at 40°C with a flow rate of 0.4ml/min. The detection of drotaverine and the internal standard was performed in multiple reaction monitoring (MRM) mode using an ion trap mass spectrometer with electrospray ionization, operating in positive mode. The human plasma samples (0.24ml) were deproteinized with methanol and aliquots of 4μl from supernatants obtained after centrifugation were directly injected into the chromatographic system. The method shows a good linearity (r(2)>0.997), precision (CV<6.3%) and accuracy (bias<5.4%) over the range of 2.24-448ng/ml drotaverine in plasma. The recovery was between 91 and 98%. The limit of quantification was 2.24ng/ml. The analysis required only a 3.0min run. The developed and validated method for the determination of drotaverine in human plasma was successfully applied in a bioequivalence study, for analyzing approximately 1000 subject's samples.