Simultaneous analysis of oxybutynin and its active metabolite N-desethyl oxybutynin in human plasma by stable isotope dilution LC-MS/MS to support a bioequivalence study

- Selective and rapid LC-MS/MS method for oxybutynin and N-desethyl oxybutynin.
- The method employs only 300 μL plasma for efficient processing by LLE.
- Six endogenous phospholipids were monitored to determine the extraction efficiency.
- First report on bioequivalence study in healthy Indian volunteers.
- Method reproducibility was ascertained by incurred sample reanalysis.