Repackaging levothyroxine sodium tablets: storage conditions to maintain stability in a hot and humid environment

Abstract

AbstractBackgroundStorage instructions for repackaging into a dose administration aid (DAA) have been included into the consumer medicines information (CMI) for some brands of levothyroxine sodium tablets. However, these storage conditions specify an ambient temperature of <25°C, which is often not representative of ambient conditions in hot and humid areas of Australia.AimThe aim of this study was to determine the physicochemical stability of two brands of levothyroxine sodium tablets, Eutroxsig (Aspen Pharma, St Leonards, NSW, Australia) and Eltroxin (Aspen Pharma), when repackaged and stored at 30°C and 75% relative humidity (RH).MethodsThe physicochemical stability of levothyroxine sodium 200 microgram tablets repackaged into DAAs and stored at 30 ± 2°C and 75 ± 5% RH for 14 days (Eutroxsig) and 28 days (Eltroxin), and under refrigeration (Eutroxsig) for 28 days, was assessed. Drug content was determined using a validated HPLC method.ResultsThe mean (± SEM) decrease in drug content in repackaged Eutroxsig tablets stored at 30°C and 75% RH for 14 days was 7.0 ± 1.0%, compared with only 2.4 ± 0.8% for Eltroxin tablets stored at 30°C and 75% RH for 28 days. When repackaged Eutroxsig tablets were stored under refrigeration for 28 days, no loss of levothyroxine sodium content was detected.ConclusionThis study clearly indicates the stability of Eltroxin tablets on exposure to hot and humid conditions, and highlights the need for pharmacists to provide information depending on the brand of levothyroxine sodium tablets repackaged.