Narcotics Cause Heartburn and Worsen GERD:Narcotics like morphine, codeine, oxycontin, and methadone cause acid reflux symptoms like heartburn and worsen GERD symptoms by causing esophageal dysfunction, slowed digestion, and opioid-induced vomiting. Though the side effects of narcotic use are a major challenge, there are strategies for preventing acid reflux, heartburn, and GERD.