Effects of excipients on swelling and drug release from compressed matrices

Polymers, and particularly hydrogels, are becoming very popular in formulating controlled-release tablets because they are excellent drug carriers. The effects of hydrophilic and hydrophobic polymers, incorporated in matrices containing soluble (propranolol HCl) or less soluble (flurbiprofen) drugs, on swelling and release kinetics were investigated. The results indicate that swelling and release profiles were affected by the amount of ingredients, the characteristics of the polymer, and the drug substances incorporated in the matrices. Swelling may influence the release rate of the drugs from the matrices. The data obtained from the in vitro dissolution study were evaluated on the basis of a theoretical dissolution equation, by linear transformation of the dissolution curve, and by the Peppas equation. The release mechanisms appeared complex and are affected by the composition of the matrix.