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Stability of sodium valproate tablets repackaged into dose administration aids


Victoria K. Llewelyn, School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia.


Objectives  Since sodium valproate, a commonly used antiepileptic drug, has been reported to be unstable in the presence of moisture, our objective was to investigate the effect of repackaging into dose administration aids.

Methods  Sodium valproate 100 mg immediate-release tablets were repackaged and stored for 56 days at accelerated conditions (40°C/75% relative humidity), room temperature (25°C) and under refrigeration (2–8°C). Samples were analysed at 3, 7, 10, 14, 21, 35, 49 and 56 days to determine chemical stability using high-performance liquid chromatography, while physical testing included assessment of weight changes and dissolution behaviour.

Key findings  The results revealed that the sodium valproate content in the tablets remained within the acceptable range of 90–110% under all storage conditions for 56 days. Physical stability, however, was not maintained, with a total weight gain of 12.36% under accelerated conditions over the 56 days. Samples stored under all conditions showed variable dissolution compared to the controls, with the amount of sodium valproate in solution following 45 min of dissolution testing below 75% for half of all the intervals determined.

Conclusions  Repackaging sodium valproate tablets into dose administration aids results in unacceptable weight variation and changes in the dissolution profiles.