I wonder if grapefruit + reduced dosage could be as effective for primary effects, but reduce side effects for some drugs.

Would be interesting to find some research in this area: most of what I can find warns of increased side effects from maintaining constant dosage.

Interesting related info: "Seville oranges, (often used in marmalades), limes and pomelos also produce this interaction. Varieties of sweet orange, such as navel or valencia, do not contain furanocoumarins and do not produce this interaction."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3589309/

Also from the NHS website is this interesting 2014 report on grapefruit juice and diabetes. In the reported study, grapefruit juice was as effective at lowering blood sugar as metformin, a leading drug for type 2 diabetes. However, this report cautions about the results - the study was not carried out on humans, but on non-diabetic mice:

Could grapefruit juice protect against diabetes?

https://www.nhs.uk/news/diabetes/could-grapefruit-juice-prot...

I don't think that's how drug pricing works. According to this report's appendix G[1], manufacturing costs are 25% of price and they count after-release R&D as part of that (and don't count pharmacy margins).

Most generic drugs probably don't cost more than a few cents a pill to manufacture, assuming the pharmacy and manufacturer make a profit on it.

In other words, it's all in the R&D and compliance costs, which grapefruit couldn't help with.

And re: doctors prescribing a combination of active ingredients that hadn't had a pharma company spend a few billion dollars studying... well, just read this[2], about how some company is making big bucks selling $300 fish oil pill bottles that had a bit of FDA compliance work (and related studies) done about them because doctors would never prescribe the $30 pill bottles that weren't filed with the FDA.

[1] http://bvssp.icict.fiocruz.br/pdf/Pharmaceutical.pdf

https://slatestarcodex.com/2014/06/15/fish-now-by-prescripti...