Specification for impurities

[ajaib5]

Can we set up the impurities specification just the double as given in pharmacoepial API monogram.

For exxample, for a API, the limits given for impurity is 0.5% in USP, but the monogram for drug product is not in USP.

So can we set ur limit for drug product as 1.0% for that impurity, without any safety data?

[JM]

No, this does not work that way. You have to see if the impurity is degradation product or not, if this is not a degradation product you can have the same limit in your product as in API. If it is a degradation product, you have to keep the limit similar to what exists in near expiry sample of already marketed formulation ( Reference listed drug).

JM

[adam]

Just to expand on one point in the above post: if you know that the material is not a degradation product, you don't have to analyze for it at all in the drug product. Just testing it in the drug substance is sufficient.

ICH guidelines are pretty clear on this (and these guidelines were actually written by the FDA - so there can be no question about where the agency stands on this).

[ajaib5]

Dear Sir,

Thanks for ur response.

Yes it is true. But i am not clear how to give limit for impurities in the begining, when the stability data may not be available for a product.

[adam]

There is no set rule, but I think a practise that is pretty common is to use the ID limit in the ICH guidelines.

[DR]

Just to expand on one point in the above post: if you know that the material is not a degradation product, you don't have to analyze for it at all in the drug product. Just testing it in the drug substance is sufficient.

ICH guidelines are pretty clear on this (and these guidelines were actually written by the FDA - so there can be no question about where the agency stands on this).

That said, you still have to show that your method is selective and specific in terms of keeping process impurities separated from degradents.