Abstract

Inclusion complexation between furnidipine (2,6-dimethyl-4-(2-nitrophenyl)- 1,4-dihydropyridine-3,5-dicarboxylic acid 3-tetrahydrofurfuryl 5-methyl diester), a calcium-channel antagonist, and ?-cyclodextrin (?-CyD) was studied in aqueous solution by using both spectrophotometric and electrochemical measurements. The phase solubility profile was classified as AL-type, indicating the formation of 1:1 stoichiometric inclusion complex of furnidipine with ?-CyD. Based on the spectrophotometric absorbance's variations, a formation constant value, Kf, of 156M -1 was determined. Electrochemical measurements using chronocoulometric experiments were used for the determination of the diffusion coefficients. In absence of ?-CyD, a diffusion coefficient value of 4.32×10-6cm2s-1 was obtained for furnidipine. The addition of ?-CyD produced a decrease of 30% for the diffusion coefficient. Formation of inclusion complexes of furnidipine with ?-CyD was proved to increase more than three times the solubility of furnidipine. © 2004 Elsevier B.V. All rights reserved.