I have taken oxycontin in the past for vascular headaches. It is a 12 hour continuous release. For example, if you take 40 mg you get 3.3 mg per hour for 12 hours. Generally, it is not prescribed for 8 hours cause if you take one after 8 hours, you still have four hours of 3.3 mg per hour left plus whatever you have just taken. I took 40 mg every 12 hours. If I had pain that would "breakthru" then I would take a fast acting 5 mg oxyIR (I think IR means immediate release). These are goon drugs for pain but be careful because since they act for 12 hours once they are in your system they are there for 12 hours. Watch your breathing and be sure itthe mediis not slowing it down. Also, don't tell anyone but your closest friends you are on oxycontin because the street value is 1 dollar per milligram. In other words, one 40 mg onycontin goes for $40 on the streets. It is enough incentive for someone to break in your house. When you throw the empty bottle away, rip the label off and tear it up so no one rummaging thru your garbage looking to steal your identity doesn't find a goldmine if he (she) rrealizes you have a cash cow (oxycontin) in your house. BEEEE CAREFUL. Nancy Stephens