Methadone is an opioid. The common side effects of the medications are Nausea, vomiting, constipation, lightheadedness, dizziness, dry mouth, drowsiness, or sweating may occur. Some of these side effects may decrease after you have been using this medication for a while. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Misuse or overdose of this medication can be fatal. Consult your doctor if you have asthma or breathing issues or any other health problems before taking this medicine.
