Stability of oral liquid preparations of methylergometrine

The stability of an oral ready to-use form of methylergometrine (0.05 mg/mL), which provides a convenient volume for administration (5 mL), was evaluated over a forty-seven-day period at different temperatures (5 degrees C and room temperature) without light in order to assign a shelf life. Methylergometrine was assayed by a stability-indicating HPLC method with diode array detection. The drug undergoes degradation under basic conditions and dry heat (50 degrees C). All the peaks of the degraded product were resolved from the standard drug with significantly different retention times. Statistical analysis proves that the method is reproducible and accurate for estimation of the intact drug. The pH of samples was monitored periodically for changes. Samples were also visually inspected for any colour change, precipitation or crystallization. At least, 96% of the initial methylergometrine concentration remained throughout the 47-day study period. Over the test period, no significant change was observed in the pH or colour of any of the samples. No degradation products were revealed. This study allowed an oral ready to use solution of methylergometrine (0.05 mg/ml) to be prepared, with a shelf life of more than one month (47 days) when stored at room temperature without light.