Opioid analgesics : The mechanism of action

Interactions with one or more subtypes of opioid receptors, in example mu-, delta-, kappa-, sigma and epsilon at supraspinal, spinal and peripheral levels, causing analgesia, and many other effects. Opioid analgesics can be full agonists of opioid receptors, namely μ (mu)-receptor partial μ-agonist and mixed agonist-antagonists have opposite effects.

Opioids act by:

• presynaptic inhibition of production of neurotransmitters C-fiber endings,
• postsynaptic suppression of evoked activity in nociceptive path or remove the remaining parts of the regulation of inhibition of nociceptive impulses.
• increased transmission of the descending inhibition of spinal nociceptive conduction.