Determination of the benztropine analog AHN-1055, a dopamine uptake inhibitor, in rat plasma and brain by high-performance liquid chromatography with ultraviolet absorbance detection.

N-Substituted 3alpha-[bis(4'-fluorophenyl)methoxy] tropanes represent a series of novel potential cocaine abuse therapeutics. AHN-1055, a member of this series, has been assessed to be the most suitable analog for pharmacokinetic studies. A sensitive and specific high-performance liquid chromatography method was developed to quantitate AHN-1055 in rat plasma and brain tissue. Reversed-phase chromatography with ultraviolet detection (lambda=220 nm) was utilized to quantitate the eluate. Plasma or brain tissue samples were prepared by liquid-liquid extraction using hexane, followed by evaporation, reconstitution in mobile phase, and injection onto an ABZ+plus column. AHN-1055 and oxprenolol (internal standard) eluted at approximately 9.9 and 5.01 min, respectively, without any interfering peaks. The calibration curves were found to be linear in the range of 25-10000 ng/ml for plasma and 50-5000 ng/g for brain (r2> or =0.999). The intra- and inter-day variabilities were < or =10% whereas the intra- and inter-day errors were < or =8.5%. Plasma and brain recoveries of AHN-1055 were 95 and 79%, respectively. Stability studies showed plasma quality control samples to be stable through at least three freeze-thaw cycles (error<3.5%), for at least 24 h when subjected to room temperature (error<3%) and for at least 30 h after loading the processed samples onto the autosampler (error<3%). AHN-1055 stock solution was found to be stable for at least 4 months when stored at 4 degrees C (error<6%). The validated method accurately quantified AHN-1055 in plasma and brain samples collected from a pharmacokinetic study consisting of an intravenous bolus in the tail vein of adult male Sprague-Dawley rats.