Stability studies and climatic zones: why packaging changes by country
The same tablet, in the same bottle, does not live the same life in Oslo and in Abidjan. That is why stability studies are run under the conditions of the country of sale, and why the pack sometimes has to change with them.
By Tecmom editorial team · 2 min read
Test the way it is stored
A stability study follows a medicine in its pack, under defined temperature and humidity conditions, to set its shelf life. The international guideline ICH Q1A sets the reference conditions: long-term conditions at 25 °C and 60% relative humidity or at 30 °C and 65%, and accelerated conditions at 40 °C and 75%.
The principle is simple: test under the conditions the product will meet, and a little beyond.
Five climates
The World Health Organization sorts countries into climatic zones in its 2018 stability guideline:
- zone I: temperate;
- zone II: subtropical and Mediterranean;
- zone III: hot and dry;
- zone IVa: hot and humid, 30 °C and 65% relative humidity;
- zone IVb: hot and very humid, 30 °C and 75%.
Each authority states the zone that applies to its territory, and therefore the study conditions it expects.
What it changes for packaging
The hotter and more humid the air, the more the pack must protect. A bottle that is enough in a temperate zone may no longer be in zone IVb: the wall lets more water vapour through when it is hot, and each opening lets in more humid air.
The levers are well known: a higher-barrier material, a thicker wall, a tighter closure, a desiccant, smaller packs. See permeability and silica gel.
A question of export
A laboratory selling in several zones must prove stability in the most demanding one it targets, or adapt its pack from one market to another. Either way, the chosen pack goes into the file. For a packaging maker, that is a reason to document the barrier and tightness of its bottles precisely. See pharmaceutical packaging.
A pack is never good in the absolute: it is good for a product, a duration and a climate. Changing country sometimes means changing bottle, and it is the stability study that says so.
Glossary
- Stability study
- Monitoring a medicine in its pack to set its shelf life.
- Climatic zone
- A climate category that sets the conditions of stability studies.
- Relative humidity
- The amount of water vapour in the air, relative to the maximum possible at that temperature.
- Accelerated conditions
- Harsher conditions that make degradation appear sooner.