Validation question

[amstrong32]

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.

[bundy5555]

You can use this approach with justification. However, be prepared to defend your approach in audits. TBH, I would just perform separate validation for DP and DS.

[smalldots]

it is better to perform the validation for DS and DP separately. it is kind of hard to justify the worst situation.

[DR]

I disagree.
Ideally, you have one method with slightly different sample preps for DS and DP. When validating, you should do recoveries on both.
All done.