Stability of Levothyroxine Sodium Tablets Marketed in Sudan

Abstract

Stability of medicinal products is the extent to which a product retains, within specified limits throughout its period of storage and use (i.e. its shelf life), the same properties and characteristics that it possessed at the time of its manufacture.
The aim of this study is to evaluate real-time stability and photo-stability of levothyroxine sodium tablets marketing in Sudan. Levothyroxine sodium tablets from different manufacturers were kept at control room temperature (23–25°C); All the samples were analysed every month using the British Pharmacopoeia (BP) HPLC method.

All tablets were kept in a closed glass dish and exposed to direct sunlight for 10 days to evaluate photo-stability using BP and HPLC methods.  The results revealed that thyroxine tablets had become out of specification (88.0, 87.0 and 87.0%) after 15, 20 and 19 months, respectively, from the date of manufacturing and lost more than 5% from initial concentration after 8–9 months; and lost about 40% of its potency after exposure to sunlight.

The shelf life of levothyroxine sodium dosage form should be <2 years to ensure that the dosage form was containing the correct dose when dispensed for use. It is evident from the analysis, sunlight has measurable effect on the stability of levothyroxine sodium even in solid dosage forms.