A SEMIAUTOMATED ANALYTICAL METHOD FOR THE DETERMINATION OF POTENTIAL ANTIHYPERTENSIVE AGENTS (CGP 48933 AND OR CGP 48369) IN HUMAN PLASMA USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A semiautomated method for the determination of two new antihypertensi ve drug candidates, CGP 48933 (I) and/or CGP 48369 (II), in human plas ma has been developed and validated. The method is based on high-perfo rmance liquid chromatography (HPLC) and uses an analog of the drug can didates, CGP 48791 (III), as the internal standard. Plasma proteins ar e precipitated with acetonitrile, the supernatant is acidified with pH 2 buffer, and both compounds and internal standard are subsequently e luted from cyclohexyl solid-phase extraction cartridges with methanol. The organic solvent is removed by evaporation under nitrogen, and the residue is reconstituted in HPLC mobile phase. Separation is achieved on an Inertsil(R) ODS-2 column (5 mum, 4.6 x 150 mm) at 40-degrees-C with fluorescence detection of the analytes at excitation and emission wavelengths of 265 and 378 nm, respectively. Specificity was demonstr ated by the lack of interfering peaks at the retention times of the dr ugs and internal standard. Recovery and reproducibility assessments in dicated good accuracy (overall mean relative recovery of 94.9%) and pr ecision (coefficient of variation (CV) less-than-or-equal-to 12.8%) fo r I over the concentration range of 50 to 5000 ng/mL, with a quantific ation limit of 50 ng/mL. Similar values were determined for II, with a n accuracy of 91.9% and precision less-than-or-equal-to 15.5%, over th e same concentration range. The method has been successfully applied t o a pharmacokinetic study in which normal volunteers received a single , oral dose of 160 mg of I.