DEFINITION of 'Bioequivalence'

A similarity between two drugs meaning that they both have the same effect on the patient. Bioequivalence means that two drugs release their active ingredient into the bloodstream in the same amounts and at the same rate. When assessing how well a generic drug works, scientists evaluate its bioequivalence to the name-brand version.

BREAKING DOWN 'Bioequivalence'

For a generic drug to get the U.S. Food and Drug Administration’s (FDA) stamp of approval, the manufacturer must prove that it is bioequivalent to the name-brand version. A drug maker must also get FDA approval before marketing or selling a different version of an approved drug. For example, it must prove that a once-a-week tablet is bioequivalent to a daily tablet. In addition, the FDA has different bioequivalence standards depending on whether the drug is taken as a pill, injection, patch, inhaler or through another method. When a generic drug is not bioequivalent to the name-brand version, it might still be approved for another use, but not be approved as a substitute for the name-brand version.

Unlike their name-brand counterparts, generic drugs usually don’t need to go through the full clinical trial process to get approved because generic drugs only have to be bioequivalent. The company applying for approval to market the generic drug only has to test the generic drug against the brand-name drug on two small groups of test subjects, draw timed blood samples from each patient, and show through statistical analysis that any difference in the drug’s bioavailability in participants taking the brand name version versus participants taking the generic version is not clinically significant.

It is easier to make a bioequivalent form of a traditional pill or injectable drug than to make a bioequivalent form of a biologic drug. As a result, the generic versions of biologic drugs, called “biosimilars,” may have to undergo clinical trials to gain approval.