A class of synthetic chemicals/drugs similar to opiates (opium derivatives) with analgesic properties. Due to binding to opiate receptors, opioids mimic opiate activity on neurons, various cells (i.e. lymphocytes), pain suppression and other neurobehavioral activity.

A substance used to treat moderate to severe pain. Opioids are like opiates, such as morphine and codeine, but are not made from opium. Opioids bind to opioid receptors in the central nervous system. An opioid is a type of alkaloid.

Any narcotic, natural or synthetic, that behaves in the body like an opium-derived drug.

Opioids are a class of drugs derived from the opium poppy (including synthetic variations) that are pain relievers with a high potential for misuse. Opioids are used to relieve pain, but they also cause an exaggerated sense of well-being and, if used too much, dependence and addiction.