Opana ER 15 mg is a Schedule II controlled substance that contains oxymorphone (which is a morphine-like opioid analgesic), used in the treatment of severe pain in patients for an extended period. Since it is a controlled substance, it may become habit-forming if you use this medication for a long time which can lead to overdose and death. Opana ER 15 mg works in the human brain by changing the way the body feels and responds to pain. It is a semi-synthetic opioid analgesic supplied in 15 mg tablet strengths; in the form of a white eight-sided pill with imprint 15 on one side of the pill. Doctors recommend the initial dose of 10 mg to 20 mg for adults every 4 to 6 hours per day but the dosage is based on your medical condition and response to treatment. Always remember to take one tablet at a time with enough water to completely swallow the tablet. Many side effects and symptoms including mood changes, anxiety, dizziness, drowsiness, backache, joint pain, weakness, abdominal cramps, insomnia, nausea, vomiting, diarrhea, constipation, headache, heart rate, etc., may develop.