Quantitative Analysis of the Effects of Drug-Base Ratio on the Physical and Release Properties of Paracetamol Suppositories
Paracetamol is available in various strengths as rectal suppositories, hence the need to evaluate the effects of drug-base ratio as a formulation variable on the physical and release properties of paracetamol suppositories formulated with a lipophilic base. Suppositories, each containing 60 mg to 500 mg of paracetamol in cocoa butter were prepared by fusion method using 1 g and 2 g capacity moulds. Physical and dissolution properties of the suppositories were determined by established methods. Quantitative effects of the drug-base ratio on physical and release properties of the suppositories were analysed using 22 factorial experimental designs. The independent and interaction coefficients of the two variables deviated from zero, indicating significant effects on the physical and release properties of the suppositories. While First-order release kinetics was observed for all the formulations, there was a significant change in the release rate constants with variation in the drug-base ratio. High proportion of base to drug ratio in the suppositories suppressed the release of the drug, suggesting the need to optimize the drug-base ratio when formulating a poor water-soluble drug like paracetamol in fatty bases.