We don't allow
speculation about which brand/generic of a drug is "best" or "strongest", because it's just that, baseless speculation. So if no one has any scientific basis for their claims (and sources to prove it) this thread will get shut down.
Some generics are actually identical to the name brand, they are even manufactured in the same manufacturing plant.
There is a difference also between if you are referring to just any different forms/brands of the same substance [in this case the drugs are not supposed to be equivalent, as one in an XR and one is an IR], or a generic that is supposed to represent a specific brand name drug [in this case if you were comparing Adderall IR and its generic version].
In the United States for example, a generic equivalent to a specific brand name drug must:
- Have the same active ingredient, quantity of active ingredient, and route of administration as the brand name product. Generic drugs do not need to contain the same inactive ingredients as the brand name product.
- Some variability can and does occur during manufacturing, for both brand name and generic drugs. When a drug, generic or brand name, is mass-produced,
very small variations in purity, size, strength, and other parameters are permitted. The FDA limits how much variability is acceptable for both.
(I can try to find out what the limits are).
- The generic drug manufacturer must do a study to show its drug is "bioequivalent" to the brand name drug. For example, they will do a study on 24 healthy people. After a person in the study takes the generic drug, the amount of drug in the bloodstream is measured, then an average is developed from all the people in the study. The average levels of the active drug in the bloodstream must be close to the same as the levels found when the brand name product is used. The generic is then assumed to have the same therapeutic action as the brand name drug.
Note: Really what these trials show is that the new drug is not inferior to an unacceptable extent, "bioequivalent" is actually a misnomer, as true equivalence (assurance that the generic drug is not any less effective than the brand name at all), could only be shown by demonstrating superiority. Because the intent of the trial is to show that the new drug is not significantly materially worse than the brand name, they are now called "non-inferiority" trials. But that too, is a misnomer, as guaranteeing that the new drug is not any (even a little) less effective than the control could only be demonstrated by showing that the new drug is superior. What non-inferiority trials seek to show is that any difference between the two drugs is small enough to allow a conclusion that the new drug has an effect that is not too much smaller than the active control. I will try to find out what the allowable difference is.
- The FDA considers "bioequivalence" sufficient to assume "therapeutic equivalence" - the equal ability of two drug forms to ease symptoms or cure disease. This assumption has been criticized [see
LA Times article].
- Generics do not have to have the same extensive clinical trials as the original brand name drug, because the results are expected to be the same, and this is why generics are cheaper.
[sources for the above: The FDA
here and
here].
[Related reading:
The FDA’s Generic-Drug Approval Process: Similarities to and Differences From Brand-Name Drugs]
Most other countries have very similar rules.
. . . . . . . . . .
According to
the LA Times:
In almost all cases, the FDA permits a generic drug to release 80% to 125% of an active ingredient into the bloodstream, compared to that released in a single dose of the original medication. That range would make little practical difference in the effect that most drugs have. And the FDA and generics manufacturers defend the allowable range of variance as the same that is permitted among "batches" of brand-name drugs.
So IF that is even true*, it sounds like there is an allowable variance
in blood levels after taking the drug of +25%/-20% compared to the brand name, BUT there is also the same variance allowed for brand name drugs. I
highly doubt there is a variance that big in the allowable amount of
active ingredient present in the pill itself.
*The
Generic Pharmaceutical Association claims:
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.
