Photochemical stability of the inclusion complexes of nicardipine with alpha-, gamma-cyclodextrin, methyl-beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin in the solid state and in solution

The inclusion behaviour of alpha-cyclodextrin (alpha-CD), gamma-cyclodextrin (gamma-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and methyl-beta-cyclodextrin (M-beta-CD) with nicardipine (NC), in solution and in the solid state was investigated. Inclusion complexes of nicardipine with cyclodextrins at a molar ratio 1 : 1 in the solid state were obtained by the kneading method. The formation of clathrates was confirmed by IR, XRD diffractometry, C-13 NMR spectra and DSC studies. Photochemical stability of NC in the solid inclusion complexes was assessed by IR spectrometry. The alkyl derivatives of beta-CD were found to slow down the photodegradation rate a little, whereas in the presence of alpha- and gamma-CD the photodegradation of NC was a bit faster than in the corresponding physical mixture. Photochemical degradation of NC in liquid inclusion complexes was monitored by UV spectroscopy. According to the slowing down effect on photodegradation of NC in liquid inclusion complexes the studied cyclodextrins can be ordered as: alpha-CD < gamma-CD < HP-beta-CD < M-beta-CD.