Full Opioid Agonists

The opioid receptors - mu, delta and kappa - are G protein-coupled receptors for the endogenous endorphins, enkephalins and dynorphins. Agonist binding couples the receptor to inhibitory Gi/Go proteins, which suppresses adenylate cyclase and inhibits N-type and L-type calcium channels; mu-mediated inhibition of voltage-gated calcium channels on central presynaptic terminals of primary afferent nociceptors is thought to be a primary mechanism of analgesia at the spinal level, and the mu receptor is the main physiological target of most clinically important opioid analgesics. This class holds the opioid agonists whose effect is not limited by a ceiling: the FDA-approved label for buprenorphine, a partial agonist, records that compared with full opioid agonists such as methadone and hydromorphone, sublingual buprenorphine produces typical opioid agonist effects which are limited by a ceiling effect, and that because of its partial agonist properties buprenorphine may precipitate opioid withdrawal in people dependent on full opioid agonists. As MED-RT populates the class its members are morphine, hydromorphone, oxycodone, oxymorphone, fentanyl and the other fentanils, codeine, hydrocodone, levorphanol, meperidine and tramadol.