I'll do my best to explain. So in chemistry, there is a thing called 'chirality' essentially this has to do with how a molecule is shaped. It's assessed by how a beam of polarized light that is passed through a molecule rotates.
There are a few different types:
Achiral, no change
Levorotary (L), Rotates anticlockwise
Dextrorotary(D), Rotates clockwise
The reason that it matters and what I was talking about above is that the sites in your body that a drug interacts with aren't universal. So if you have a (L) version of a drug that might have different effects and interactions than a (D) version.
A 1:1 mix of both (L) and (D) is called a racemic mix.
When you are talking about Brand name drugs, you're typically discussing a particular mix (e.g. Adderall XR is a 3:1 (D):(L) mix) or a particular conformation. That is not necessarily true with generics which may have a different ratio of (D):(L).
To give an example of how different the effects can be: Penicillamine (L) is used in the treatment of primary chronic arthritis.
Penicillamine (D) not only has no therapeutic effect, it is highly toxic.
If generic drugs have a different L:D ratio and L molecules have a different effect than D molecules, then surely the generic has a different effect and result than the brand name which would make or the other work better. Wouldn’t that come up and be an issue leading to either reformulating the generic to better match the brand name, or pulling the generic altogether?
> To give an example of how different the effects can be: Penicillamine (L) is used in the treatment of primary chronic arthritis. Penicillamine (D) not only has no therapeutic effect, it is highly toxic.
I think, as a layman, Thalidomide is probably a good striking example.
One chirality does what it says on the tin. The other causes babies to be born missing limbs and with other birth defects.
In theory, if we could produce Thalidomide with only the correct isomer, it would not only be effective but 100% safe for pregnant women.
