FORMULATION AND EVALUATION OF METRONIDAZOLE EFFERVESCENT GRANULES

Efferevescent granules are granular dosage form of drug in a dry mixture usually composed of effervescents like sodium bicarbonate, citric acid and tartaric acid. Effervescent granules when added to water, the acids and the base react to liberate CO₂, resulting in effervescence. A combination of tartaric acid and citric acid is used as an effervescent base rather than either acid alone because when tartaric acid is used alone, chalky friable granules are produced and citric acid alone results in sticky mixture to difficult to granulate. The weakly acidic drugs when formulated in effervescent granular forms exhibit increased absorption from gastric environment as most of the drug remains in unionized form. The bitter taste of the drug can be masked by the effervescence that was produced when the formulation is mixed with water. Effervescent granules of weakly acidic drug, metronidazole were formulated by melt granulation process in which  low melting binder composition comprising of a polymer and a hydrophobic meltable binder like PEG 4000 and cetyl alcohol is used. Formulations having varying composition of effervescents and meltable binder composition were prepared and evaluation tests for carr’s index, effervescence cessation time, in-vitro drug release studies were performed. From the observations,  the formulation having 5% meltable binder, cetyl alcohol was found to have excellent flow properties, 100% drug release and high effervesce cessation time.