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Abstract

The incorporation and release of sulfadiazine, paracetamol, diazepam, quinine hydrochloride, and doxycycline hydrochloride in and from rectangular slabs of highly crosslinked citric acidglycerol copolymer matrix have been described. The release of the drugs in phosphate buffer of pH 7.4 and at 37°C was followed spectrophotometrically. After an initial burst, the first three drugs were released up to 4 days and the last two drugs up to 7 days at almost constant rates. The erosion profile of the drug-free matrix and the release characteristics of the drug-loaded slabs under physiological conditions indicate hydrolytic erosion of the slab from the surface as well as from the bulk. It has been suggested that the zero-order release of the drugs was possible due to a balance between the decreasing release rate by diffusion through the matrix and the increasing release rate because of increasing polymer permeability resulting from gradual crosslink cleavage.