Oxycontin is a powerful opioid pain medication that is available in both immediate-release and extended-release formulations. The extended-release formulation is designed to provide around-the-clock relief from moderate to severe pain for 12 hours or more. Oxycontin is typically taken every 12 hours. Common side effects of Oxycontin include nausea, vomiting, constipation, drowsiness, dry mouth, and headache. More serious side effects may include slowed or shallow breathing, confusion, seizures, and extreme sleepiness. If you experience any of these side effects, stop taking Oxycontin and seek medical help immediately.