Bioequivalence of Drugs: Drugs with Multiple Indications

The concept of therapeutic equivalence (TE) in drugs with multiple indications is complex. A generic drug may be therapeutically equivalent to a brand-name product for one specific indication, but this doesn't necessarily mean it's equivalent for all other indications. Evidence of TE in one patient group and bioequivalence shown in healthy volunteers can support—but not confirm—TE for other indications. However, definitive proof requires individual clinical studies for each indication due to the variable characteristics of drugs and their impact on different patient populations. For instance, a drug may dissolve quickly and be fully absorbed in patients with a normal GI tract pH, rendering particle size and formulation changes irrelevant to bioavailability. However, the same drug may have different bioavailability in cancer patients due to slower dissolution in the GI tract, which has a higher pH. So, when a drug treats multiple conditions, we can only assume it’s bioequivalent across all of them if supported by rigorous clinical studies.