Re: How this forms addiction - the levels prescribed are for a 12 hour period, but since the drug only lasts 8 hours, a patient is getting a dose above the recommended level that it should last.

Marketed: 120mg over 12 hours or 80mg over 8 hours

Reality: People that take the 120mg over 12 hours realize it only lasts 8 hours thus they are taking 40mg more than they should be on the schedule that makes sense to them to avoid pain.

Well, the reality seems to be even worse.

Rather than taking 40mg at the end of the day, the drugs companies caution doctors to prescribe more medication initially rather than give any indication that the drug only lasts for 8 hours.

They care more about their approach to marketing, than the efficacy of the prescription schedule.

It's this that creates addicts: the extreme high of the unneeded extra initial dosage, followed by a lower low when the drug runs out.

What nine_k meant is that 120mg is too much, so the person gets a tiny buzz at first. But instead of acclimating with a consistent dose as you suggested, they wait 12 hours until the drug has worn off, causing a crash. Then they repeat the high/low cycle, causing an addiction.

why would that form an addiction?

Psychologically. Instead of constantly feeling okay (the pain is gone, you keep getting a prescribed amount and no more), you are reminded every few hours that with the drug the life is good, and without it the life is miserable. But you cannot alleviate the pain unless you break the rules (the prescription).

Once the prescribed regime is broken, and the psychological restraint is broken, too, there's little left to stop the usage from spiraling up, to an overdose.

because you experience repeated cycles of pain, take pills, then relief, then pain, take pills, then relief.