ò-Naltrexamine, or 6ò-naltrexamine, is an opioid receptor antagonist related to naltrexol and naltrexone. It has served as a parent pharmacophore for irreversible antagonists of the ü-opioid receptor (MOR) such as ò-chlornaltrexamine (ò-CNA) and ò-funaltrexamine (ò-FNA). Naltrexamine itself is a neutral antagonist of the MOR and the ô-opioid receptor (DOR) with similarly high affinity for both receptors.