A fast and sensitive UHPLC-MS/ MS method for the determination of N-butylscopolamine in human plasma: application in a bioequivalence study

We have developed and validated a fast and sensitive ultra high-performance liquid chromatography with positive ion electrospray ionization tandem mass spectrometry method for determining N-butylscopolamine levels in human plasma using propranolol as an internal standard.The acquisition was set up in the multiple reaction monitoring mode with the transitions m/ z 360.3.138.0 for N-butylscopolamine and m/ z 260.2.116.1 for IS.This method uses a liquid-liquid extraction process with dichloromethane.The analyte and IS were chromatographed on a C18, 50x2.1 mm, 1.7 mu m column through isocratic elution with acetonitrile- 5mM ammonium acetate (adjusted to pH 3.0 with formic acid).The method was linear in the 1-1000 pg/ mL range for N-butylscopolamine and was selective, precise, accurate and robust.The validated method was successfully applied to perform a bioequivalence study of the reference (Buscopan r, from Boehringer Ingelheim) and the test sample coated-tablet formulations (from Foundation for Popular Remedy), both containing 10 mg of N-butylscopolamine bromide administered as a single dose.Using 58 healthy volunteers and accounting for the high intra-individual variability confirmed by statistical calculations (38%), the two formulations were considered bioequivalent because the rate and extent of absorption (within 80-125% interval), satisfying international requirements.