Purpose: To prepare and evaluate new sustained release formulations of indomethacin based on extracts of propolis (bee glue).
Methods: Standardization of propolis (bee glue) extracts was performed by high performance liquid chromatography (HPLC) and determination of the values of fat and fixed oils. Several indomethacin capsule formulations (F1 - F18) containing varying amounts of chloroform (0.75 - 75 mg) and ethanol extracts (30 - 75 mg) of propolis were prepared. The dissolution rate of the formulations was evaluated by USP dissolution (rotating basket) method I and the release data subjected to various kinetic models. Probable interaction between the drug and propolis extracts was studied by differential scanning calorimetry (DSC).
Results: The results show that, although the release rate of formulations F1 - F7 did not show any significant difference (p <0.05) compared to F18 as blank, the other formulations did. DSC results indicate that incorporation of propolis extract in the formulations lowered indomethacin melting point by between 5 and 30 ºC, indicating interaction between the drug and the waxy extract. Kinetic analysis of the in vitro release data of the formulations showed that the best-fit drug release model varied with the drug:propolis extract ratio of the formulations.
Conclusion: Formulation F13 (with equal proportion of drug and bee glue extract) came out best from the dissolution test for indomethacin extended-release capsules as it exhibited zero order kinetics. This fpormulation is therefore suitable for further development as a matrix formulation for controlled release.
