This probably isn’t quite what you’re asking, but of all the weird medication scams out there, I think the scammiest might be Silenor.

It works like this: doxepin (brand name: Sinequan) is an antidepressant from the 1970s, rarely used these days. A typical dose would have been about 100 mg. Some people noticed that very low doses of doxepin (maybe 10 mg) would put people to sleep. So even though as an antidepressant it’s been mostly replaced by SSRIs and stuff, for the past 40 years psychiatrists have used very low doses off-label as a sleeping pill. Not all psychiatrists did this, because you have to open a pharmacology textbook to realize that this sort of odd way of using an obsolete medication is even an option, but enough psychiatrists that it was a reasonably common practice. And a cheap one too - a supply of the 10 mg dose costs about $10 per month.

In 2010, Somaxon Pharmaceuticals rebranded low-dose doxepin as a new sleeping pill, Silenor. They spent $170 million to get it approved by the FDA at a dose of 6 mg (this non-round number will be important), with a nice FDA label saying “THIS PILL IS APPROVED FOR SLEEP”. Now they are selling it for about $450 per month.

You might ask: if you can get a month’s supply of 10 mg pills of a certain drug for $10, and a month’s supply of 6 mg pills of the exact same drug for $450, surely everyone will just buy the $10 version, right? Well, some people do, other people don’t; sales of Silenor are about $5 - $10 million/year.

Why? Well, about half of doctors don’t realize Silenor is just doxepin. The other half realize it, but have no incentive to prescribe the cheaper pill and can’t be bothered to do so. Part of this is that the official FDA studies showing doxepin promotes sleep were only done on the 6 mg dose. Everyone knows from personal experience that the 10 mg dose also makes you sleepy, there’s no pharmacological reason to believe the 10 mg dose is much different from the 6 mg dose, but if you prescribe the 10 mg dose then annoying people might say “Oh, you’re just EXTRAPOLATING from a study done on the 6 mg and your own anecdotal experience? Guess you must HATE EVIDENCE-BASED MEDICINE.”

(the blog Thought Broadcast does a good job looking into some of the actual pharmacology here - see https://thoughtbroadcast.com/2011/03/18/thank-you-somaxon-pharmaceuticals/ )

The good news is that even $10 million/year sales of Silenor aren’t enough to recoup the company’s initial investment in getting it through the FDA, so they’re going to make a huge loss from the whole affair and maybe this will discourage other people from trying the same thing. In the future, I expect pharma companies will stick to their usual strategy of at least taking a stereoisomer or a metabolite of an old medication before claiming that they’ve found something new and exciting we should all pay ten times as much for.