accelerated stability testing

Accelerated stability testing speeds up the ageing of a medicine so its likely future can be glimpsed in months rather than years. Like leaving bread in a warm, humid place to see how fast it spoils, the product is deliberately stressed — held hotter and more humid than normal — to make degradation happen on a timescale a developer can wait for.

Under the ICH framework, the standard accelerated condition for many products is 40 degrees Celsius and 75 per cent relative humidity for six months, often with an intermediate condition (such as 30 degrees and 65 per cent) as backup. The amount of degradation seen is fed into kinetic and Arrhenius modelling to estimate behaviour at the normal storage temperature and to support a provisional shelf life while the slow real-time study at the labelled condition continues to run in parallel.

Accelerated data are powerful for ranking formulations, flagging unstable candidates early, and justifying an initial expiry date — but they are predictions, and the long-term real-time study at the actual storage condition remains the definitive evidence.

An honest caveat: acceleration only works when heating merely speeds up the same degradation pathway. If high temperature melts a wax, converts a polymorph, dries out an emulsion, or switches on a reaction that never occurs at room temperature, the accelerated result can badly misrepresent real-life stability.