Photostability (ICH Q1B)
Testing a product's response to light exposure, using defined visible and near-UV doses, to decide whether light-protective packaging or labelling is required.
Doses that count
Not less than 1.2 million lux hours of visible light and not less than 200 watt hours per square metre of near-UV, run on exposed samples alongside protected controls.
Where it bites
Contrast media, certain cytotoxics and most vitamin C cosmetic systems are light sensitive. If the protected control holds and the exposed sample fails, the answer is packaging — amber glass, cartons or secondary wrap — not reformulation.
Related terms
Where this applies
Contrast Media, Cosmetic Formulations
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