The stability of diluted cough syrups dispensed from commercially available cough mixture was studied. 4-Preparations of various composition were prepared and stored up to 2 months at 5℃, 25℃, and 40℃, respectively. The concentration of dl-methylephedrine·HCI in the samples was determined by high-performance liquid chromatographic assay at 0, 7, 14, 28, 56 days. The pH of the samples was measured and the samples were also inspected for precipitation, turbidity, odor and stench, at above times, respectively.
The concentration of dl-methylephedrine·HCI in the samples remained within 90％ of the initial concentration throughout the study period. But the pH and the visual changes were noted at each diluted samples within test period. As a result, diluted cough syrups were relatively stable for 2 weeks at 5℃, and it is more desirable that it could not be diluted because of its stability problem.
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