If a Drug Product didn’t have a USP Monograph but one did exist in the EP, would the FDA accept an EP Method in a submission as long as it was appropriately qualified?
You can adopt EP method to claim in-house method and also check the all impurities mentioned in Drug substances are must elute in this method. also performed the degradation of drug product and check the mass balance. if mass balance are achieved so method are prove as a stability indication method and validate. you can submit this method to FDA as an in-house claim.