ENANTIOMERIC BIOANALYSIS OF SIMENDAN AND LEVOSIMENDAN BY CHIRAL HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

rac-Simendan, -3-pyridazinyl)-phenyl]hydrazono]propanedinitrile, and t he levorotatory enantiomer levosimendan, are drug candidates intended for the treatment of congestive heart failure. An enantiospecific high -performance liquid chromatographic (HPLC) method suitable for determi nation of the ratio of the enantiomer concentrations in blood plasma s amples was developed. Direct resolution of the enantiomers was achieve d by using a chiral beta-cyclodextrin stationary phase in reversed pha se mode. With an eluent containing 24-33% of methanol in a 0.5% (v/v) triethylammonium acetate buffer, pH 6.0, and a now rate of 1 ml/min, a resolution (1.2-1.6) adequate for the determinations was achieved. By using UV detection, the relative concentration of the enantiomers in plasma was assessed down to 10 ng/ml. For the racemate, the results in dicated a slightly enantioselective disposition and plasma protein bin ding in rat, dog, and man. The pure enantiomer, levosimendan, was foun d not to isomerize in vivo. (C) 1996 Wiley-Liss, Inc.