All generic drug manufacturers are required to go through the FDA’s Abbreviated New Drug Application (ANDA) process. This is an extensive testing process where the generic drug manufacturer must prove the following:

  • Generic drug is pharmaceutically equivalent in its dosage form and release mechanisms.
  • The manufacturer can make the drug correctly and consistently.
  • The active ingredients are the same as the brand name drug. 
  • The generic drug exerts the same effects in the body as the brand name drug.
  • Any inactive ingredients used are safe.
  • The drug is stable over time.


In addition to the requirements above, the FDA routinely inspects manufacturing facilities for compliance.


What Does Bioequivalence Mean?

It is important to discuss the level of bioequivalence, or expected action of the drug in the body, that is required by the ANDA process for the generic drug product to be able to be brought to market.


The FDA uses a statistically calculated range to determine if drug products have the same bioequivalence or action in the body. Both generic and brand name drug manufacturers must meet these requirements. For example, brand name drug manufacturers are required to show bioequivalency in the brand name drugs in different batches of the drugs that are produced. It has been reported that on average there is less than a 4% difference between generic and brand name drugs in terms of bioequivalence.  


Difference Between Generic Drug Manufactureres

So, why do patients sometimes report an increase in side effects or a difference in expected outcomes when switching to generics? In the case of side effects, sometimes it can be due to the inactive ingredients, or fillers, used to manufacture the drug. Though this is a rare occurrence, for patients who are sensitive to gluten, lactose or certain dyes, this can definitely be a problem.


For other patients, perception of generics by the patient and even the prescriber can influence the patient’s perceived reaction to a new drug. Having a negative view of generics can potentially have a patient focus on how they may not being feeling the same with the generic drug versus the brand name drug. If this view were to continue and the patient stops taking the drug, the expected outcome from the generic drug is different from the brand name drug since the drug is not being taken anymore.


However, the possibility does exist that for the smallest percentage of patients the generic drug may not work the same. If a patient has any concerns that a drug is not working as well and his or her disease state or symptoms are worsening, a discussion should be had with the doctor or prescriber of the medication.


Patients should always remember to not take what they read on-line as the true picture of how a generic drug behaves versus a brand name drug. While it may seem like a lot of patients are complaining, the reality is there are thousands to millions of patients taking the same exact generic drug getting the same expected results as the brand name drug. The testing required by the FDA supports this fact and patients should feel confident that the generic drugs they are taking will work as well as the brand name drugs (or other generic manufacturers of the same drug).