Post-dispensing stability surveillance: Stavudine

BACKGROUND: Stavudine, a thymidine nucleoside, is a reverse transcriptase inhibitor, which is extensively used in the treatment of HIV infected patients. According to the World Health Organization (2006), stavudine must be stored in well closed containers and be protected from light. In addition, the manufacturer recommends that stavudine be stored below 25°C in a tightly closed container. However, because of the stigma associated with the disease condition, patients may attempt to hide their medication by storing the drug in more anonymous packaging, which may not comply with these storage requirements. Furthermore, the high temperature and humidity conditions found in sub-tropical areas such as Durban, KwaZulu-Natal, place additional environmental stress on the drug. Research has shown that stavudine can degrade to thymine under hydrolytic, oxidative and photolytic conditions. Therefore, this study investigated the stability of stavudine in packaging other than that used by the manufacturer and under temperature and humidity conditions that were higher than those recommended by the manufacturer. METHOD: Stavudine capsules were placed in different types of packaging and then subjected to different temperature and humidity conditions. At two week intervals the capsules were analysed using HPLC (high pressure liquid chromatography). RESULTS: Stavudine capsules stored in packaging other than that used by the manufacturer and under temperature and humidity conditions that are higher than those recommended by the manufacturer showed significant degradation. CONCLUSION: Patients taking stavudine stored under sub-optimal conditions may ingest less than the required dose of stavudine. This can lead to drug resistance and treatment failure.