Interaction of terfenadine with cyclodextrin

ABSTRACT

The potentiality of molecular interaction of terfenadine with alpha- cyclodextrin [alpha-CyD] and beta-cyclodextrin [beta-CyD] was investigated by spectrophotometric methods. Differential UV spectrophotometry revealed an increase in the optical density of terfenadine in presence of cyclodextrins. Application of the continuous variation method to spectrophotometric measurements revealed equimolar stoichiometry of interaction. The apparent solubility of the drug in presence of alpha- and beta-CyD was investigated and the stability constants [Kc] were estimated from the straight portion of the phase-solubility diagram and found to be higher for the drug beta-CyD system pointing out that the larger the cyclodextrin cavity, the more profitable it would be to include that, bulky terfenadine molecule. Complexes of the drug alpha- and beta- CyDS were prepared and the process of complexation was also monitored by IR spectrophotometry. The dissolution profiles of the drug, physical mixtures of the drug and cyclodextrins as well as the prepared complexes showed enhanced drug dissolution properties of the prepared complexes compared to physical mixtures or the drug per se. The dissolution rate of the drug-beta-CyD complex was found to be higher than that of alpha-CyD complex which runs parallel with their stability constants confirming the great role played by cyclodextrin complexation in enhancing the dissolution rate of the drug