Effect of Processing and Sintering on Controlled Release Wax Matrix Tablets of Ketorolac Tromethamine

The objective of present study was to evaluate the effect of processing methods and sintering condition on matrix formation and subsequent drug release from wax matrix tablets for controlled release. Ketorolac tromethamine and compritol were processed with appropriate diluent using either dry blending, spray drying, partial melt granulation or melt granulation.The tablets were then sintered at 80°. The sintered tablets were characterized by their physical parameters and in vitro dissolution tests. The micro-morphology and wettability of the tablets was also investigated. It was evident that different processing methods for identical formulation significant impact the release profile of drug. Sintering further retarded drug release and its effect was related to the manufacturing processes. Scanning electron microscopy showed that heat treatment redistributed the wax and formed a film-like structure covering drug and excipient particle. The contact angle of tablets made by dry blending, spray drying and partial melt granulation methods increased after sintering, while that of tablets made by melt granulation remained constant. Drug release from the wax tablets with or without heat treatment was best described by the Higuchi equation. Different processing methods produced different matrix structures that resulted in different drug release rates. Sintering retarded drug release mainly by decreasing the porosity of the matrix. Contact angle measurement and SEM analysis indicated that heat treatment caused the wax to melt, redistribute, coat the drug and diluents and form a network structure. Differential scanning calorimetry studies ruled out the occurrence of solid solution of the drug during sintering condition.