Accelerated Degradation Experiment
Conditions
Procedure A: |
30 days exposure at 50 °C and 100% relative humidity. |
Procedure B: |
30 days exposure at 50 °C and 100% relative humidity followed by 5 days at 70 °C and 100% relative humidity. |
Appearance of the substance
The substance, originally in the form of a yellow to light brown powder, changes after procedure A into a yellow powder and after procedure B into a dark orange-yellow powder.
Gain of moisture
None after procedures A and B.
Tests on the sample subjected to accelerated degradation
Thin-layer chromatography can not be carried out since the solubility of the substance in methanol is only 4 mg/ml. This solubility decreases after procedures A and B, and an insoluble residue is left. No solvent can be found to dissolve this residue in order to carry out the test.
Through separation and weighing the insoluble residue in dimethylformamide the degradation after procedure A is assessed at 20% and after procedure B at 50%.
The degradation is confirmed by microbiological measurement of the soluble portion of the sample subjected to procedures A and B. The activity obtained is 3000 U/mg, compared to 4405 U/mg for the reference substance of nystatin.
Conclusion
Nystatin is subject to decomposition under accelerated degradation conditions.
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