Are Generic Drugs as Effective as Name Brands?

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Blood levels of brand and generic drugs do not differ by 20%-25%.  Rather, based on two major analyses by FDA of hundreds of products, blood levels of brand and generic products may differ approximately 3.5% -4.0%.  This is the same variation that would be found if two different lots of the brands product were compared to each other.

In general, two formulations whose relative mean rate or extent of absorption differ by -20% to +25% or less are considered bioequivalent. This does not mean that a generic product can differ by potency, blood level, or the amount of active ingredient by as much as 20% less or as much as 25% more from the brand drug, which is how these numbers are frequently misinterpreted. To clarify these often-confused figures, the FDA wrote that the -20%/+25% statistical criteria “is widely misunderstood. It actually represents acceptable bounds on the 90% confidence intervals around the ratio of the mean results for each of the two products....” In other words, if the information were graphed, the data should fall within a specific range of the mean. Another misperception is that this range applies only to generics. It actually applies to both brands and generics. Additionally, by law, generic products MUST contain the same amount of active ingredient as the brand product.  Therefore, the claim that generics may be formulated to contain 10% more or less than the brand is false.

The same tests and criteria, which are used to confirm the sameness of a generic to a brand drug, also are used to confirm the sameness of the brand to itself, if the brand manufacturer makes a change in the manufacture of that brand drug, which is a common practice during the life-cycle of the brand product. “Post-approval, the innovator may change the scale of production runs, equipment, manufacturing processes, formulations, dosage forms, ingredient specifications, source of supplies, and method of synthesis of the active ingredient. FDA accepts the results of the innovator’s bioequivalence study to demonstrate ‘sameness’ between the ‘old’ and the ‘new’ product using the same bioequivalence criteria as that used for evaluating generic drugs.”

Similarly, the American Medical Association scientific board recognizes that these statistics are “widely misunderstood” and physician publications have attempted to dispel the myth.