Buy OxyContin acts on the central nervous system (CNS) to relieve pain. Buying OxyContin extended-release capsules or tablets should not be used if you need pain medicine for just a short time, such as when recovering from surgery. Do not use this medicine to relieve mild pain or in situations when non-opioid medication is effective. This should not be used to treat pain that you only have once in a while or “as needed”. Chronic moderate to severe pain, such as in osteoarthritis, back pain, and some other conditions: Healthcare providers prescribe extended-release versions of oxycodone, such as Xtampza ER or Order OxyContin, for cases where other approaches aren’t expected to be successful.