Opioids are a class of drugs that derive from, or mimic, natural substances found in the opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, including pain relief. The terms 'opioid' and 'opiate' are sometimes used interchangeably, but the term 'opioid' is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain...