A recent article suggested that Purdue Pharmaceuticals dosing guidelines pretty much guaranteed addiction to OxyContin, by advising doctors to only ever prescribe the drug at 12 hour intervals despite the fact that it wore off more quickly for a large number of patients.
When patients complained about the drug wearing off early, Doctors were advised to not adjust the schedule but instead increase the dosage.
The pain-pleasure-reward cycle when the drug wears off early is what creates the physical addiction, and increasing the dosage only made it worse.
Purdue insisted on a 12 hour schedule because that is the marketing differentiater between OxyContin and generic opiates.