Interestingly, while on-patent medications in the US tend to be significantly more expensive than elsewhere, generics in the US tend to be less expensive than generics available elsewhere.

in the US, we call these 'generics'

Now look into the places that manufacture these generic versions. Not all factories are equal, and some are not of the best of reputations.

Additionally generics can differ in terms of the inactive ingredients or coating or other stuff. See e.g. https://news.osu.edu/all-generic-drugs-are-not-equal-study-f...

Those are available in America too

But prices are going up. Look at the statements your insurance company provides about the reimbursed "cost" of covered generics:

Some experts report that PBMs overcharge for generics; The Wall Street Journal estimated that Cigna and CVS Health, both of which own PBM services, are able to charge prices for specialty generic drugs that are 24 times higher than what manufacturers charge.

https://www.americanprogress.org/article/5-things-to-know-ab...

Huge caveats. The drug manufacturer gets over a decade of market exclusivity which bars the selling of generic versions of the medication, which they can then extend again if they find another distinct use case for the medication (3 more years). This is why the Vyvanse generic took so long.

So this must be worldwide. It seems like the patents held by big pharma are the root of the corruption. What is the guarantee here? That the chemicals are pure, or just that the companies are getting their cut?

Generic is the English word for it. The brand name drugs have a limited time patent and they are supposed to help cover the initial research and development costs of bringing that drug to market.

Generics can only be made after the patent expires. And due to pressure from western countries, these are enforced worldwide.

Which takes over a decade and can be extended multiple times if they find more uses for the drug.

That's what he said. Brazil is in (South) America.