The effect of surfactant above and below the critical micelle concentration (CMC) and the mathematical models used to determine the kinetics of drug release from the matrix system

Abstract

The liberation of propranolol HCl from a controlled release matrix, containing the hydrophilic polymer, sodium carboxymethylcellulose (NaCMC) and the hydrophobic polymer, Eudragit RL 100 (RL 100) as excipients, was studied. The influences of surface active agents on the dissolution rate of the drug were examined. Tablets were made by direct compression methods. The dissolution tests were performed by using the basket method. The incorporation of the cationic surfactants within the matrices increased the drug release until the critical micelle concentration (CMC). While, after the CMC, the increase in drug release was to a lesser extent. The incorporation of the anionic surfactants reduced the release rate of the drug from the matrices. At the CMC, the percent of drug release from the matrices were approximately the same with the matrices without the surfactants. While an increase in drug release was observed above the CMC of the anionic surfactants. The data obtained from in vitro drug release studies were plotted according to three kinetic models to study the release kinetic. These were zero order release, the first order release and the Higuchi equation. Zero order release of the drug was observed in all the formulations. The release mechanism was influenced considerably by the ratio of the excipients. Key words: Propranolol HCl, controlled release, critical micelle concentration (CMC), dissolution, dissolution rate kinetics, surfactant.