a validation question

[darasc0211]

Hi, I am validating a stability indicating HPLC method for assay and impurities for both drug substance and drug product. All impurities listed in the drug substance and drug product specifications are the same and their criteria are the same.

Can I only validate spiked recovery for impurities in drug product which I think is the worst case scenario and waive the spiked recovery for impurities in drug substance?

Thanks.

[tom jupille]

My response would be "no". While I agree that drug product is the worse case, matrix effects can work both ways (i.e., helping or hinderinf recovery), so there is no guarantee the recoveries will be the same.