Opna ER is classified as an opioid pain reliever and is prescribed for the management of moderate to severe chronic pain. Unlike immediate-release opioids, OPANA ER has an extended-release formulation that provides continuous pain relief over an extended period. However, it's worth noting that OPANA ER can also be habit-forming and addictive if misused or taken in excess. It's essential to follow your doctor's instructions carefully and not take more than prescribed or share with others. Common side effects of OPANA ER include nausea, constipation, dizziness, drowsiness, headache, and dry mouth. If you experience any concerning symptoms or have questions about this medication, don't hesitate to reach out to your healthcare provider for guidance. As with any medication, it's important to follow your doctor's instructions carefully and inform them of any concerning symptoms or changes in your health while taking Opana ER.