What Is Bioequivalence?

Bioequivalence means that the active ingredient in a generic medicine is absorbed into the body at the same rate and amount as in the brand-name product. This ensures that the generic delivers the same therapeutic effect as the brand counterpart and can be safely substituted with the brand product. Bioequivalence gives consumers, patients, physician and pharmacist the assurance that FDA-approved generic medicines provide the same medicine and the same clinical results, with the same safety profile, as their brand counterparts.

Federal law requires that, in order to receive FDA approval, generic drugs contain the same active ingredient as the brand-name counterpart, be the same strength and dosage form (tablet, capsule, etc.), and have the same route of administration (oral, topical, injectable, etc.). It is important to know that bioequivalent drugs, whether brand-to-brand or generic-to-brand, work in the body in the same way and provide the same safety and efficacy profile. In short, generics provide the same medicines, but at a more affordable cost.

Key Points

  • Each year more than 2.6 billion prescriptions are filled in the U.S. using generic versions of brand pharmaceuticals. This compares to approximately 1.2 billion brand-name prescriptions dispensed annually in the U.S. With close to 70% of all prescriptions being filled with generics, patients, pharmacists and physicians all recognize the tremendous value of generic medicines.
  • There are no published studies or scientific evidence to show that the interchangeability of a generic for a brand name drug presents difference in safety or effectiveness for the patient. FDA has confirmed on several occasions that bioequivalence requirements for generics and brands are rigorous and ensure that approved generics are therapeutically equivalent to their brand counterparts.
  • Based on FDA analysis of hundreds of bioequivalence studies, FDA has determined that small differences in blood levels -- less than 4% -- may exist in some cases between a brand and its generic equivalent. But FDA has repeatedly pointed out that this minor difference is no greater than the difference that may exist between two different manufactured batches of the brand drug.
  • There is a frequent misstatement regarding the bioequivalence of generic drugs, which asserts that blood levels of the active ingredient in generic drugs may vary from minus 20% to plus 25% compared to the brand. This simply is not true and any generic with a difference that dramatic would never be approved by the FDA. The 20% to 25% margin is one part of a complex statistical calculation used to help measure the bioequivalence. In no way does it represent the actual difference in the amount of active ingredient a patient's bloodstream, which FDA has determined is typically less than 4% between generic and brand or between two different batches of a brand drug.
  • FDA's approval process for generic drugs is equally as stringent as the process followed to approve brand drugs. The rigorous chemistry, manufacturing and controls phase is applicable to both new brand drugs and generic drugs. Labeling and testing requirements also are the same for both brand and generics. The same FDA field inspectors evaluate the manufacturing facilities for generics and for brand products, using the same standards, to ensure compliance with all good manufacturing practices. The only meaningful difference between the generic and brand approval process is that human and animal clinical studies to show safety and efficacy are conducted for new brand drugs, whereas bioequivalence studies are used in place of clinical studies in approving generics. It should be noted however, that brand drugs use bioequivalence studies during the approval process or after it is commercially available.
  • Generic drugs are less expensive than brands in large part because generic manufacturers do not have to conduct costly clinical trials to test the safety and effectiveness of a generic version of a drug that has been safely and effectively used for several years. Rather, generic pharmaceutical companies perform smaller studies to confirm equivalence to the brand product. Moreover, generics do not spend hundreds of millions of dollars in advertising and promotion.
  • Some minor differences between brand and generic drugs are permitted. For example, a generic drug may have a different shape, size or color compared to the brand product. However, bioequivalence testing assures that the generic drugs will have the same safety, efficacy and therapeutic effect as the brand product.
  • As in all situations, patients are advised to seek counsel of their physician or pharmacist on issues related to their medication.

Experts Agree - Generics Offer Same Safety and Effectiveness

According to the FDA: "[G]eneric drugs...are just as safe and just as effective as their brand-name counterparts, and they are a cost effective way of achieving substantial savings."

"[A] generic drug is identical or bioequivalent to a brand-name drug in dosage form, safety, strength, route of administration, quality, performance characteristics and intended use."

According to the American Medical Association (AMA): "[O]ne of the primary ways physicians can practice cost-effective prescribing is by offering patients a generic medicine when one is available."

According to the managing editor of Best Buy Drugs, sponsored by Consumer Reports: "Switching to generic whenever possible is, quite simply, one of the clearest paths to reducing health care spending in the years ahead."

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