An impurity limit is not one number. It is a question of which framework owns the impurity, what your maximum daily dose does to the arithmetic, and whether the product is even inside the guideline's scope. This works all three out and shows the rule it used. ICH Q3A for organic impurities in a new drug substance, Q3B for degradation products in the finished product, Q3C for residual solvents, Q3D for elemental impurities by route, and M7 for the mutagenic ones, which run on an acceptable intake rather than a percentage and land orders of magnitude lower. Nothing you type leaves the page.
● your technical inputs stay in this browserThis is a teaching instrument, not a regulatory document. It computes thresholds from published ICH guidelines and shows its working. It does not replace your toxicologist, your quality unit, or a conversation with a regulator, and a threshold is the start of an argument about an impurity rather than the end of one. Verify every number against the guideline before you rely on it.
Changes whether ICH M7 applies.
Every threshold below is a function of this number.
Q3C and Q3D work on this, not on the dose of the active. Different number.
Q3D limits are route dependent.
Used by ICH M7 only.
A framework shown as out of scope is a result, not an error. It means the guideline itself excludes this product class, and that the impurity still has to be controlled by an argument you build rather than by a threshold you read off a table.
Regulatory tables are written in words like up to and including 2 g/day, and the whole value of a calculator is that it reads those words the same way every time. These run on load. If any of them fails, the number above it is not to be trusted.