Design and evaluation of microporous membrane coated matrix tablets for a highly water soluble drug

Microporous coated matrix tablet consists of a microporous membrane which is produced directly from a nonporous polymer coating during transit in the gastro-intestinal tract. In the present study, efforts have been made to develop and evaluate the in-vitro performance of a matrix embedded microporous controlled release system to deliver a drug with high aqueous solubility (> or =3 g/ml), high pK(a) (> or =9.0) and low molecular weight (<500 Da). The matrix embedded core tablets were prepared and coated using film former (2% w/w) and different pore formers (1-20% w/w of film former) such as plasticizer (PEG 4000), surfactant (Tween 80) and polysaccharide (Dextran) in a conventional coating pan. The tablets were evaluated for various physical parameters, coat tensile strength and in-vitro drug release characteristics. The ethyl cellulose films suppressed the initial burst effect in drug release more than cellulose acetate and polymethacrylates films. PEG 4000 was found to be most effective plasticizer and pore former in controlling drug release, followed by Tween 80 and dextran. The prepared formulations provided prolonged and zero-order drug release.