Analgesics for moderate to severe pain

Opioids are defined as substances that act by binding to opioid receptors in central nervous system neurons (as a key fits into the lock). All opioids have a comparable spectrum of action, but differ in their intensity of effect and side effect profiles. Opioids are similar in their structure to endorphins (opioids produced by the body itself, hormones that abate and/ or suppress pain).

 Currently opioids are classified based on the intensity of pain treatment for:

  • Moderate pain
    As weak opioids e.g. tramadol, tilidin + naloxone, codeine
  • Severe and very severe pain
    As strong opioids e.g. morphine, oxycodone, hydromorphone, fentanyl, buprenorphine

Analgesic effect

  • Opioids activate descending inhibitory pathways in the brain.
  • Opioids affect other supraspinal structures (structure above the spinal cord) of pain processing (in particular the thalamus and limbic system), thus altering the emotional assessment of the pain (pain is still perceived, but is no longer felt as being unpleasant or threatening).
  • In the spinal cord opioids bind to pre- and postsynaptic opioid receptors, inhibit transmitter release (presynaptic receptors) and on the postsynaptic side they affect the transmission of the stimuli.