Regulation of impurities in drug substances and products

Are qualification assays sufficiently
sensitive to detect an impurity p y when the
test employs the new drug substance
(DS) containing t i i th the iimpurity? it ?
In general, g endpoints p examined in animal toxicology gy
studies, especially of short duration (2 - 4 weeks)
are insensitive.
If the DS was nontoxic and tested up to 2 g/kg, 3
mg/kg of the contaminant would be tested. Even
generally toxic chemicals such as
cyclophosphamide and dimethylnitrosamine would
probably b bl not t bbe ddetected. t t d
Toxicity of the DS further limits detectability of
impurity.
Food and Drug Administration