STABILITY OF METRONIDAZOLE BENZOATE IN SUSPENSIONS

A stability-indicating HPLC assay method has been developed to quantif y metronidazole benzoate in suspensions. A study of the stabilities of two suspensions (16.0 mg/ml) of metronidazole benzoate in commerciall y available vehicles, Ora-Plus and a mixture of Ora-Plus and Ora-Sweet , showed that both suspensions were stable for at least 90 days at roo m temperature. The mobile phase required to elute metronidazole benzoa te contained 40% acetonitrile versus approximately 10% for the free ba se. The solubility of the ester in water at 25-degrees-C was found to be approximately 0.1 mg/ml versus 10 mg/ml for the free base. The este r did not hydrolyse significantly to the free base after storage for 8 h at 37-degrees-C in simulated gastric fluid, and 5 h at 37-degrees-C in simulated intestinal fluid. The bitter tasting metronidazole may n ot be satisfactorily substituted with its tasteless ester in the treat ment of local gastrointestinal infections.