S8.3 Opioid Analgesics

Question 1

What are the effects of opioids?

Answer 1

Act as analgesics - relief of moderate to servere pain

Question 2

Outline the ‘Gate theory’ of opioids

Answer 2

Pain transmitted to substantia gelatinosa (dorsal horn) and neurotransmitter Substance P released.
Opioids inhibit release of Substance P from nerve terminals, this inhibits descending pathways from higher centres in the brain

Question 3

Name 3 endogenous opioid peptides

Answer 3

Endorphins, Enkephalins, Dynorphins

Question 4

Name 3 opioid receptors

Answer 4

μ - mu (all opiates have high affinity for this)
δ - delta
Κ - kappa

Question 5

Outline the mechanism of opioids

Answer 5

Bind to opiate receptor (Gi), Inhibits adenylyl cyclase, Decreases cAMP (delta).
Causes decreased presynaptic influx of Ca2+ (kappa), so reduced neurotransmitter release.
Reduced transmission of nociceptive (pain) impulses, and postsynaptic hyperpolarization occurs (increasing K+ efflux, mu)

Question 6

What are the ADRs of opioids?

Answer 6

Constipation, vomiting, Respiratory Depression, dependence (withdrawal symptoms) and develop tolerance (need higher dose)

Question 7

What can be given for opiate overdose?

Answer 7

Naloxone

Question 8

Give some examples of opioids

Answer 8

Oral Codeine, Oral Tramadol, Morphine, Fentanyl patch

Question 9

What is needed to covert codeine to morphine?

Answer 9

CYP2D6