Time-release to begin with was the strategy to re-patent a prescribable habit-forming API (Active Pharmaceutical Ingredient) whose underlying patent itself had already expired.
Turned out to be even more of a gold mine since the FDA approved formulations where each tablet simply contained way more of the API than it had on the label.
Full detailed data from the clinical trials supported the labeling for each tablet to show the amount from that tablet that would be released into the bloodstream when taken as directed, not the actual full amount of API in each tablet.
For the "taken as directed" dosing to be reliable enough for doctors to correctly gauge how much habit-forming toxic API their patients were absorbing compared to established & generic non-time-release formulations, the target is for the time release pills to have quite a bit of API remaining at the baseline upon excretion.
But this is an API that opiate addicts crave and it didn't take long for them to figure out they could simply crush the pills to ingest the full amount of API a tablet contained.
On the black market this escalated each pill to the top shelf category.
For addicts and chronic pain patients building a progressive tolerance they can't get enough, and this is the regular kind of opiate API that has always fomented eventual overdose when the increases are not curtailed and the toxic effects become much more prominent or fatal.
For any patient on generics who wanted _more drugs_, if they got switched to Oxycontin at the same dose they were a happy camper. Until they wanted even more. But multiple time-release pills were not in the prescribing guidelines so Purdue escalated by stepping up to the plate and developing stronger-dose product in the same time-release formulation.
This was a sign that so many people were building up a tolerance where it took more API to give them the same perceived effect.
The non-addicted occasional consumer of these powerful pain pills could sell their surplus for more each year. The financial incentive to refill prescriptions is greatest for those who don't actually take any of the pills. The Sacklers got richer at the same rate as the drug dealers too, since they raised the pharmaceutical price in step with the increases in street price.
The growing financial economy paralled the spread of the tolerance-building consumption habit, so realistically the demand was stronger than that from all of the ultimate consumers' habits by a large margin.
Opium wars had been fought over this kind of thing.
Doctors, nurses, patients, addicts, narcotics agencies were raking in the bucks like there was no tomorrow, and even those who were not benefitting by one dime were not going to stop.
Sacklers simply declared opium wars and the casualties are still mounting.