What Is The Difference Between Brand And Generic Drugs?

In our latest question and answer, we discuss the difference between brand and generic drugs.

What Is The Difference Between Brand And Generic Drugs?
Sep 22, 2017

Jack asked

What is the difference between brand and generic drugs? I'm concerned the drug I'm taking may not work well.

At a glance

  • Generic drugs work the same as brand-name drugs and are approved by the FDA.
  • A generic drug is the same as a brand-name drug in dosage, safety, effectiveness, strength, stability, and quality.
  • Although the active ingredient in a generic drug is the same as the brand, the inactive ingredients may be diffierent.


Hello and thank you for your question!

This is one of the most common questions we get and we're happy to help provide some clarity.

The point I always try to get across to people is the difference between a brand and generic drug is NOT like the difference between a box of Fruit Loops and a store brand.

The FDA requires rigorous 'bioequivalency' testing to ensure a generic drug is within a certain statistically acceptable margin for both the rate and extent of absorption of the drug when compared to the brand name drug.[1]

A generic drug will only receive approval if it is within this acceptable margin, and is then considered to be equivalent to the brand name drug in regard to dosage, safety, effectiveness, strength, stability, and quality. 

I would also like to point out that one of the common counseling points a pharmacist will give you when you get a generic drug for the first time is: "This is the same medication you have been taking but it may look different because it is coming from a different manufacturer."

How can the medication be the same if it looks different? The answer is that generic drugs, while they contain the same active ingredient, can have different fillers and other inactive ingredients.

What Is 'Bioequivalent' Mean?

A generic drug is considered therapeutically interchangeable with a brand-name drug if testing determines it is bioequivalent.

Bioequivalent, for the record, means that the rate and extent of absorption (i.e. how fast and how much) is the same for the generic as it is for the brand name.

So per the definition by the FDA, the generic drug has to absorb just as fast, and as completely as the brand-name drug.

Now nothing is ever perfect (even different batches of brand-name drugs differ in their exact percentage of active ingredients), but the FDA has acceptable ranges for bioavailability between brand and generic drugs, and that explanation goes beyond the scope of this answer (as it involved some pretty in-depth statistics such as confidence intervals, etc...).

Suffice to say, the brand and generic versions of the same drug are pretty darn close. In fact, generic medications have the same quality standards brand name ones.

Why Do Brand And Generic Drugs Look Different?

Brand and generics do look different though. This is because the inactive ingredients can be different (inactive ingredients meaning the ingredients that have no effect such as fillers and binders in the tablet).

These different inactive ingredients are taken into account during testing.

Brand Vs. Generic

So, are there situations where you may want to stick on a brand-name drug versus a generic?

There is some controversy surrounding this, but one situation where it may be prudent to stay on a brand name drug is if you have already been taking it (i.e. are stable on it) and the drug is considered a 'narrow-therapeutic index drug.

These drugs are used for disease states where a small change in dose can make a big difference in effect. Disease states where this can be the case include epilepsy certain mental health conditions.

Overall though, for most drugs and conditions, generic drugs are safe, effective, and cost-saving alternatives to their brand-name counterparts.

Do You Have To Request A Generic?

Most states have what is known as 'mandatory generic substitution' laws where your pharmacist will be legally required to dispense the generic drug for its brand-name counterpart if it is available.

This is done as a cost-saving measure, and, as mentioned above, the generic drug should work the same as the brand name.

If your provider wants the brand-name drug dispensed over the generic, they must indicate this specifically on the prescription. It must be said however, that most insurance companies do not cover brand names if a generic is available.

Thanks again you again for reaching out to us!

  • A Primer on Generic Drugs and A Primer on Generic Drugs and Bioequivalence, FDA
  • Generic Drugs, FDA

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