I may or not have mentioned the basic concept already in some or another of the alternative apocalyptic scenarios treads as I'm nursing it for some time but I would likely like to see someone with more proficiency of language (and hopefully talent) to play with it so...
The good news: extensive research in aging prevention have had very definitive results (and perhaps sooner than expected, that is, virtually today/tomorrow). A medication/treatment is developed, simple enough at the point of use (probably not literally a single pill, but close in concept) that won't make you noticeably younger outright, wouldn't make you immortal or regrow your teeth or anything like that, but "just" promise to freeze the effects we understand as general aging for about fifty years. There's also no known reason why a repeated use should be an issue (although there's really no point of doing it double backback-to-back as the effects won't stack like that), but given the re-supply at the right time someone could potentially live, not necessarily forever as nobody canceled diseases and accidents and all such, but given good luck and good care a long time. Is all those claims really true will take a couple centuries to verify, obviously, but the hype is great.
As is the price of the stuff, round a million $US a use (let's say in 2000' dollars to fix it harder) is the bottom bid. Worse, that price is entirely justified, not just a premium. It uses some real rare stuff, and is labor intensive to produce by highly trained specialists, individually for each customer (and not readily transferred to other user, the effects may be unpredictable at best, and possibly lethal) and has short shelf life if any. You can't really mass produce or even stockpile it, so no matter how much money you throw at it it's ought to remain rather exclusive.
Obviously, you want to take it as young as possible, well, maybe not quite as a kid (although, in theory, why not), but young people doesn't often have that kind of money really available. Of course, you could, in theory, take out a credit, million on fifty years isn't even anything that much, really. And there's people willing to make just such a deal, buy you the drug for you on an agreement, but the terms they make are bit harsher than simply a credit, they would like to claim they own you.
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The collapse as such aren't given, and won't be swift or readily straight forward causality chained on the fact of the drug as such, but would the current order of things, or any order at all really survive introducing of something such? I don't think. There would be riots. There would be terrorists. The inequality would skyrocket so much and be so sharply obvious. And yeah, I really believe the slavery deal would be irresistible for enough people to be nearly unavoidable to be introduced. And add it as given at least some would make it with silent intent to cheat out of it, one way or another.
