A risk-based approach to establish stability testing conditions for tropical countries.

The external stability risk factors heat and moisture are evaluated with respect to the development of pharmaceutical products intended to be marketed in tropical and subtropical countries. The mean daily temperatures and dewpoints measured four times per day at selected places in Southeast Asia, South America, China, Southern Africa and the Caribbean are used to calculate the daily and monthly fluctuations of temperature and partial water vapour pressure, the mean kinetic temperature and the relative humidity. Based on these data, the hottest and the most humid place in each country or region are identified to reflect the worst case for the specific region. A formula to calculate safety margins for temperature and partial vapour pressure is introduced taking into consideration the difference between measured meteorological parameters and the stability testing conditions. An appropriate long-term stability testing condition is proposed for each selected country, related to the worst case for each specific region and the safety margins, as well as its classification in either Climatic Zone IVA or IVB. (c) 2006 Wiley-Liss, Inc. and the American Pharmacists Association