Chiral analysis of bambuterol, its intermediate and active drug in human plasma by liquid chromatography-tandem mass spectrometry: Application to a pharmacokinetic study

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for simultaneous chiral analysis of an antiasthma drug bambuterol, its key intermediate monocarbamate bambuterol and its active drug terbutaline in human plasma. All samples were extracted with ethyl acetate and separated on an Astec Chirobiotic T column under isocratic elution with a mobile phase consisting of methanol and water with the addition of 20 mm ammonium acetate and 0.005% (v/v) formic acid at 0.6 mL/min. The analytes were detected by a Xevo TQ-S tandem mass spectrometer with positive electrospray ionization in multiple reaction monitoring mode. The established method has high sensitivity with the lower limit of quantifications of 25.00 pg/mL for bambuterol enantiomers, and 50.00 pg/mL for monocarbamate bambuterol and terbutaline enantiomers, respectively. The calibration curves for bambuterol enantiomers were linear in the range of 25.00-2500 pg/mL, and for monocarbamate bambuterol and terbutaline enantiomers were linear in the range of 50.00-5000 pg/mL. The intra- and inter-day precisions were <12.4%. All the analytes were separated in 18.0 min. For the first time, the validated method was successfully applied to an enantioselective pharmacokinetic study of rac-bambuterol in 8 healthy volunteers. According to the results, this chiral LC-MS/MS assay provides a suitable and robust method for the enantioselectivity and interaction study of the prodrug bambuterol, the key intermediate monocarbamate bambuterol and its active drug terbutaline in human.