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Opiates define a large class of drugs with structural similarity to morphine (a major analgesic found in opium extract from the poppy flower). The term opioid is often used interchangeably with the term opiate. However, the term opiate more properly refers to the natural narcotic compounds (alkaloids) found in the resin of the opium poppy (Papaver somniferum). Use of the term "opioid" should be reserved for semi-synthetic substances that are derived from the opium poppy or made completely in the lab. Opiates/opioids include the following drugs:
  • Morphine: Contin, Oramorph, Roxanol
  • Oxycodone: Oxycontin, Percoset
  • Hydrocodone: Codan, Hycodan, Hydromet
  • Hydromorphone: Dilaudid
  • Loperamide: Imodium
  • Methadone: Dolophin

Opiates activate opiate receptors found in the central nervous system (CNS). The endogenous ligands for these receptors are endorphins and endorphin-like peptides. Interestingly, opiates do not alter the pain threshold of nerve endings nor do they affect the conductance of nerve impulses (like anesthetics do). Instead, analgesia is mediated through changes in the perception of pain at the spinal cord and higher levels in the CNS. There is no ceiling effect of analgesia for opiates. The emotional response to pain is also altered with opiate use. Opiates are often referred to as euphoric medications since they can elevate mood. They also can induce physical and emotional dependence and addiction.