Abstract
This study aimed to prepare a colon drug delivery system using dry‐coated time‐controlled disintegration wax matrix tablets. Indomethacin was used as a model drug. Behenic acid and lactose were used as coating materials. The effects of lactose content and pH of the dissolution medium on drug release were investigated. The porosity and the tortuosity of the surface matrix layer were calculated. Four formulations of wax matrices containing different percentages of lactose in the surface layer, i.e. 70, 65, 60 and 55, were prepared. The lag times of indomethacin release from the matrices in 0.05 M phosphate buffer pH 7.4 were 50, 162, 294 and 539 minutes for formulations containing 70, 65, 60 and 55% lactose, respectively. The release of drug from formulations containing lactose in the range of 60–70% in different media, i.e. 0.05 M phosphate buffer pH 7.4, 0.05 M alkaline borate buffer pH 8.5 and in the case of pH changed media from pH 1.3 to pH 7.4, was not different (p=0.1). This implies that the different environment in the gastro‐intestinal tract will not affect the release of this delivery device. The required lag time period can be met by varying the amount of lactose.