L23 Drugs for Pain Flashcards
What are the naturally occurring opioid compounds?
morphine
codeine
What are the synthetic opioid compounds?
methadone
fentanyl
What are Endorphins?
endogenous opioid peptides
NT and hormone peptides made in the brain that have similar activity to morphine
-synthesised and released from nerves
Name 3 endorphins
beta-endorphin
enkephalins
dynorphin
Physiological roles of endogenous opioid peptides
Analgesia: inhibit pain neurotransmission and perception of pain
Intestinal mobility regulation
Pharmacology of endogenous opioid peptides
-act as opioid receptors GCPRs
-peptides, rapidly metabolised do not pass through BBB
not useful as therapeutics
Opioids in the nociceptive circuit
Peripheral nerve transmission
In the periphery mu opioid agonists inhibit the relaying of pain to the dorsal horn
inhibiting the upwards relaying of the pain signal
Action of mu opioid agonists
pre and post synaptic
Presynaptic: inhibition of Ca influx of AP
decreased NT release
Post synaptic: mu-opioid receptor activation increase in K conductance K+ eflux-hyperpolarising
decrease postsynaptic response to excitatory neurotransmission
Morphine mu agonist on the CNS
- Analgesia
- Euphoria
- Respiratory depression
- miosis pupil constriction
- Antitussive cough suppression
Periphery
- constipation
- bronchoconstriction, mast cells
How is morphine usually given? and why?
given iv or im
due to low bioavailability and hepatic metabolism
Heroin
analgesic, pneumonia, TB, sedative for coughs
Addictive bc:
High lipid soluble prodrug, rapid entry into the CNS
Metabolised rapidly in the brain heroin-> morphine
Methadone
orally active
slow onset
treatment for opioid dependance
withdrawal reaction less intense but prolonged
Naloxone
opioid receptor antagonists
Treat opioid overdose
Affinity for all opioid receptors
Rapid hepatic metabolism, given iv
Codeine
less potent than morphine orally active little or no euphoria and respiratory depression constipation antitussive-reduce coughing
Fentanyl
short half life
surgery- procedure related pain
used for strong acute pain
least constipating opioid
