RELATIONSHIP BETWEEN SWELLING AND DRUG RELEASE IN A HYDROPHILIC MATRIX

Hydroxypropylmethylcellulose (HPMC) is widely used for controlled-release preparations. The process of drug release is controlled by matrix swelling and polymer dissolution. This study examines the mechanism of behaviour of HPMC in a polymer-drug directly-compressed matrix. The results obtained show that the swelling of HPMC which can be described by first-order kinetics is affected by concentration and viscosity grade of the polymer. This swelling action of HPMC in turn is controlled by the rate of water uptake into the matrices. An inverse relationship exists between the drug release rate and matrix swelling rate. This implies that HPMC swelling is one of the factors affecting drug release. The swelling behaviour of HPMC is therefore useful in predicting drug release.