Advil and Motrin are two products with differences in inactive ingredients that are analytically comparable. They are however legally distinct. If Motrin slips

Advil and Motrin are two products with differences in inactive ingredients that are analytically comparable. They are however legally distinct. If Motrin slips on QC, you don't get to sue the manufacturer of Advil. So, what are the legal distinctions? Is this legally distinct product actually available and what are the distinctions, for instance, regarding liabilities?