Physico-chemical properties and stabilities of the highly potent calcium antagonist benidipine hydrochloride.

(+/-)-(R*)-2,6-Dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3, 5-dicarboxylic acid (R*)-1-benzyl-3-piperidinyl ester, methyl ester hydrochloride (benidipine hydrochloride, KW-3049), a highly potent calcium antagonist, was examined to clarify its physico-chemical properties, i.e. melting point, spectra (UV, IR, NMR, MS), X-ray diffraction pattern, thermal analysis, solubilities, pKá, partition coefficient and chromatography (TLC, HPLC). The stabilities of KW-3049 were studied under various conditions by HPLC. KW-3049 in solid state was very stable to heat and moisture, and fairly stable to light.