Ultrasonic and electrochemical studies of the interactions of the drug chlorocyclizine hydrochloride with α-cyclodextrin and surfactant micelles

Abstract

Using a drug-selective membrane electrode it has been shown that the cationic drug chlorocyclizine hydrochloride forms a 1 : 1 inclusion compound with α-cyclodextrin in aqueous solution. The drug also forms mixed micelles with cetyltrimethylammonium bromide, and the partition coefficient of the drug between aqueous and micellar phase was estimated using sound velocities. The kinetics of both processes have been measured using ultrasonic relaxation and it is found that the rate constant for the formation of the 1 : 1 inclusion compound is a factor of ca. 40 times lower than the corresponding rate constant for drug association with the mixed micelle. In both cases one would expect both the bimolecular processes to be diffusion controlled. The reasons for the difference in rate constants are discussed.