26
Opioids, opioid antagonists
and antimigraine agents
Learning objectives
Upon completion of this chapter, you should be able to:
1.
Outline the gate theory of pain and explain therapeutic ways to block pain using the gate theory.
2.
Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse
reactions and important drug–drug interactions associated with opioids and antimigraine agents.
3.
Discuss the use of the different classes of opioids, opioid antagonists and antimigraine agents across the
lifespan.
4.
Compare and contrast the prototype drugs morphine, naloxone, ergotamine and sumatriptan with other
drugs in their respective classes.
5.
Outline the care considerations, including important teaching points, for people receiving an opioid, an
opioid antagonist or an antimigraine drug.
Glossary of key terms
A fibres:
large-diameter nerve fibres that carry peripheral impulses associated with touch and temperature to the spinal cord
A-delta fibres:
small-diameter nerve fibres that carry peripheral impulses associated with pain to the spinal cord
C fibres:
unmyelinated, slow-conducting fibres that carry peripheral impulses associated with pain to the spinal cord
ergot derivative:
drug that causes a vascular constriction in the brain and the periphery; relieves or prevents migraine headaches but
is associated with many adverse effects
gate control theory:
theory that states that the transmission of a nerve impulse can be modulated at various points along its path
by descending fibres from the brain that close the “gate” and block transmission of pain information and by A fibres that are able to
block transmission in the dorsal horn by closing the gate for transmission for the A-delta and C fibres
migraine headache:
headache characterised by severe, unilateral, pulsating head pain associated with systemic effects, including
GI upset and sensitisation to light and sound; related to a hyperperfusion of the brain from arterial dilation
opioid agonists:
drugs that react at opioid receptor sites to stimulate the effects of the receptors
opioid agonists–antagonists:
drugs that react at some opioid receptor sites to stimulate their activity and at other opioid receptor
sites to block activity
opioid antagonists:
drugs that block the opioid receptor sites; used to counteract the effects of opioids or to treat an overdose of
opioids
opioid receptors:
receptor sites on nerves that react with endorphins and encephalins, which are receptive to opioid drugs
opioids:
drugs, originally derived from opium, that react with specific opioid receptors throughout the body
pain:
a sensory and emotional experience associated with actual or potential tissue damage
spinothalamic tract:
nerve pathway from the spine to the thalamus along which pain impulses are carried to the brain
triptan:
selective serotonin receptor blocker that causes a vascular constriction of cranial vessels; used to treat acute migraine attacks
Test your current knowledge of opioids, opioid antagonists and antimigraine agents with a PrepU Practice Quiz!
Simulation-based learning
On completion of the chapter, consider the scenario of Doris Bowman (Part 2) who arrives in the recovery room after
undergoing major abdominal surgery and is complaining of pain. Consider Doris’ pain management in this case.
How might the concepts learnt in this chapter apply more broadly to post-operative pain management?
Then, work through the second scenario of Marilyn Hughes (Part 2) who has had a recent fall. Consider how the
concepts learnt in this chapter relating to pain management apply to her case.
