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Generics and Bioequivalence

As the debate about health care in the United States continues forward, the term “generic drugs” has become rather commonplace. What are generic drugs? Are they safe to use? Why do we have them? And what is bioequivalence? All of these are common questions that I hope to answer with my post today.

What are generic drugs?

Generic drugs are “store-brand” drugs that are exact copies of the “name-brand” drug. If you have been shopping at the grocery store recently you might see the following two items in the breakfast isle:

Toasted Oats (left) and Cheerios (right)
Toasted Oats (left) and Cheerios (right)

Cheerios (pictured on the right) is a name brand cereal made by General Mills. Toasted Oats, on the other hand, is a store-brand or “generic” cereal that is intended to have the look and feel of Cheerios. Although these cereals may be similar, they likely are not exactly the same. In fact, most people can tell a difference between the name-brand Cheerios and any store-brand cereal. There are differences because there is no requirement for the Toasted Oats to be identical to the Cheerios. Anyone can make a cereal that looks like Cheerios and sell it. This is why food companies guard their food recipes so closely. If someone gets their recipe it will be very easy to copy the food and potentially take market share away from the brand-name food.

In 1984, the “Hatch-Waxman Act” [Public Law 98-417] was signed into law in the United States. This law allowed the Food and Drug Administration (FDA) to regulate the marketing of “generic” drugs that are identical in composition and clinical efficacy as the “brand-name” drug. Thus, similar to the cereal example, a company can create a copy of the brand-name drug and sell it in the open market. But this copy must meet stringent criteria established by the FDA to ensure that the generic drug has the same clinical efficacy as the brand-name drug.

Are they safe to use?

As mentioned above, generic drugs are required to be identical to their brand-name counterparts in composition and clinical efficacy. Thus generic drugs are just as safe as their brand-name counterparts. In fact, the manufacturing controls required for generic drugs are identical to those required for brand-name drugs.

Why do we have generic drugs?

Generic drugs are designed to offer competition in the pharmaceutical market in the United States. After the patent protection period ends on a name-brand drug, other companies can make generic copies of those drugs. Often these “generic drug companies” are able to sell the generic drug at a significantly discounted price compared to the name-brand drug. This is possible because generic drug companies have much lower research and development costs. Often generic drugs acquire >90% of the market within 2-3 years after introduction.

What is bioequivalence?

The FDA decided that a comparison of drug levels in the systemic circulation would be the best way to show that a generic drug is identical to a brand-name drug. The type of analysis to show this is called bioequivalence. See my previous post for a definition of equivalence trials. In a bioequivalence trial, systemic drug levels are measured following administration of both the brand-name and generic drugs. If those systemic drug levels are similar (±20%) then the generic drug is considered bioequivalent to the brand-name drug. More specifically, the 90% confidence intervals for of the ratio of generic drug to name-brand drug must lie between 80-125% (which is ±20% on the logarithmic scale).

If you would like additional reading, the FDA website has quite a bit of excellent information on generic drugs.

To learn more about how our clients are using the IVIVC Toolkit to accelerate generic drug development, please read this case study.


Nathan Teuscher
By: Nathan Teuscher
Dr. Teuscher has been involved in clinical pharmacology and pharmacometrics work since 2002. He holds a PhD in Pharmaceutical Sciences from the University of Michigan and has held leadership roles at biotechnology companies, contract research organizations, and mid-sized pharmaceutical companies. Prior to joining Certara, Dr. Teuscher was an active consultant for companies and authored the Learn PKPD blog for many years. At Certara, Dr. Teuscher developed the software training department, led the software development of Phoenix, and now works as a pharmacometrics consultant. He specializes in developing fit-for-purpose models to support drug development efforts at all stages of clinical development. He has worked in multiple therapeutic areas including immunology, oncology, metabolic disorders, neurology, pulmonary, and more. Dr. Teuscher is passionate about helping scientists leverage data to aid in establishing the safety and efficacy of therapeutics.

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