Buying OxyContin OC 20 mg online is a prescription medication that contains oxycodone, an opioid mainly used to manage moderate to severe pain.OxyContin is prescribed for chronic pain management, particularly in patients who require continuous, long-term opioid treatment. It's designed for extended-release, providing pain relief over a 12-hour period.The lower dose 20 mg tablet is typically prescribed for patients who have developed a tolerance of opioids.