Americans are wasting billions a year on name-brand pills

This webpage by the FDA [1] is also a simple and easy resource about generic drugs.

The basic fact about generic drugs is that they have to contain the same active compound(s) and they have to match the bioavailability (active compound presence in the blood or other targeted region). If the generic drug fits this and is FDA-approved, then it can be sold.

The composition of a pill is complex. There is the active compound, but there are also many other compounds that are needed to make the pill into a discrete structural unit, instead of a fine white-ish powder, the native form of many organic molecules. See [2] for a common example. The composition of these ingredients can vary dramatically between the brand name drug and generics. I know somebody who is allergic to a number of generic drugs, but is fine with the brand name drug. This is presumably due to different fillers used to make the pill.

In some cases, the fillers used in the generic are very similar to those used in the brand-name drug. However, in many cases, they are different and it is incorrect to say that they are identical. However, in the majority of cases, it really does not matter, and Americans are probably wasting billions a year. But in some cases, buying the brand-name is necessary.

[1]: http://www.fda.gov/drugs/resourcesforyou/consumers/buyingusi...

[2]: https://en.wikipedia.org/wiki/Mannitol

It is worth nothing that some cancer patients can become sensitized to Mannitol and become allergic to it. This may be a result of chemotherapy.

I know that Glucochrome eg is more powerful than its generic knockoffs. Also, this article http://isteve.blogspot.com/2013/05/red-pill-indian-generic-d... talks about how the FDA operates on trust, to the point that foreign generics makers (at least the example given) can and do drive trucks through it.