The term opioid refers to natural, semisynthetic and synthetic medications that relieve pain by binding to opioid receptors in the nervous system. The term includes all agonists and antagonists with morphine-like activity. Opioid switching is the change from one specific opioid to a different opioid or from one administration route to another if pain control is inadequate or side effects are a problem. Opioid switching has been studied in patients with refractory cancer pain. The National Comprehensive Cancer Network (NCCN) suggests consideration of opioid rotation or switching in the case of inadequate pain control, significant adverse events, or issues such as drug cost. Switching opioid route has been examined for its effect in managing constipation.