Mechanisms of chlorpheniramine maleate release from hydrophilic swellable polymer systems

The main objective of this work is to attempt to understand better the mechanism of release of highly water soluble drugs from a swellable polymer and to quantify the amount of drug released. Tablets containing 10% w/w drug, hydroxypropylmethylcellulose E4M (10% w/w, 20% w/w and 30% w/w), 1% w/w magnesium stearate and quantity sufficient to 100% w/w with Lactose Fast Flo as diluent were prepared using the direct compression method. The amount of drug released due to Fickian diffusion and non-Fickian diffusion (polymer relaxation) was quantified at different time intervals. In order to determine if the drug release was Fickian diffusion or non-Fickian diffusion, the exponent n obtained from the equation: Mt/M yen = Ktn was calculated. It was found to be above 0.5 for restricted and unrestricted systems indicating non-Fickian diffusion. Also, the approximate contribution of Fickian diffusion and polymer relaxation to the non-Fickian anomalous release process was calculated. The data obtained from one tablet surface and all surfaces exposed to the dissolution medium demonstrated that Fickian diffusion predominated for the first hour. After one hour of testing dissolution, the relaxational mechanism predominated. The percent drug release from restricted matrices at 6 hours of dissolution testing was 77.9% by polymer relaxation and 27.9% by Fickian diffusion.