Legally, bioequivalence of different versions of a drug can vary by what percentage?

Bioequivalence refers to the requirement that different formulations of a pharmaceutical drug (such as a brand-name drug and its generic counterpart) deliver the same amount of active ingredient into the bloodstream within a specified timeframe. In the context of the question, the legally permissible variation in the bioequivalence of different versions of a drug is typically established by regulatory bodies. These standards ensure that generic drugs can be used interchangeably with brand-name products without significant differences in terms of efficacy and safety.

The correct answer indicates that a 20 percent variation in bioavailability is acceptable. This means that the generic formulation must fall within 80% to 125% of the effect of the brand-name version to be considered bioequivalent. A 20% range allows for minor fluctuations that can occur due to different manufacturing processes without compromising the drug's therapeutic effect. Therefore, this standard supports patient safety and ensures that patients can rely on generics as effective substitutes for brand-name drugs.

In contrast, other percentages offered in the choices fall outside the typical ranges established by regulatory authorities, thus reflecting limits that are either too strict or not representative of industry standards regarding bioequivalence assessment.