L40- Opioids Flashcards
list the endogenous opioids and their source
source- POMC (Proopiomelanocortin)
- endorphins
- enkephalins
- dynorphins
(1) are the clinically relevant opioid receptors, with (2) signaling and (3) as the end result
µ, κ, δ receptors:
-Gi receptors —> although no dec in cAMP
Presynaptic: closes Ca channels (no influx –> no neurotransmitter release)
Postsynaptic: opens K channels (inc efflux –> inc depolarization –> dec APs)
name the opioid receptors related to the following:
- (1) analgesia (supraspinal and spinal)
- (2) sedation
- (3) psychotomimesis (psychosis / delusions / delirium)
- (4) dec repiration
- (5) dec GI motility
1- µ, κ, δ 2- µ, κ 3- κ 4- µ 5- µ
list the all the CNS effects of opioid (therapeutic and adverse)
-analgesia
- sedation (µ, κ)
- euphoria
- respiratory depression (µ)
- cough suppression // anti-tussive
- n/v
- miosis (µ, κ)
- truncal rigidity
list all the PNS effects of opioids (therapeutic and adverse)
- hypotension
- constipation
- pruritus (via Histamine release)
- contraction of biliary smooth muscle – contraindicated with biliary colic
Opioids:
- (activates/inhibits) ascending pain pathway
- (activates/inhibits) descending pain pathway
1- inhibits
2- activates (serotonergic, adrenergic)
describe opioid effect on ascending pain pathway
Normal: stimulus in peripheral nerve–> neurotransmitter release –> spinal cord neuron fires AP to signal Pain
With Opioid:
- presynaptic Ca channels blocked –> no neurotransmitter release
- postsynaptic K channels opened –> inc depolarization, no AP
ascending pathway blockade = Spinal Analgesia
describe the normal functions of descending pain pathway and then how opioids change this pathway
- Serotonergic and Adrenergic neurons send descending fibers in order to inhibit ascending pain pathway
- Interneurons (GABAergic) will release GABA on Serotonergic and Adrenergic neurons to inhibit APs and their release of neurotransmitters –> disinhibition of ascending pain pathway => pain
OPIOIDS: inhibit neurotransmitter release in Interneurons –> therefore no inhibition of Serotonergic and Adrenergic fibers –> inhibition of neurotransmitter release in ascending pathway
descending blockade = supraspinal anagelsia
list the opioid agonists (not mixed):
- indicate most potent
- indicate least potent
- *morphine (hydromorphone, oxymorphone): most potent µ agonist + weak κ, δ agonist
- fentanyl (µ)
- meperidine (µ)
- methadone (µ)
- **codeine (hydrocodone, oxycodone): weak µ, δ agonists
- heroin
- levorphanol
list the mixed opioid agonists (describe general activity)
µ antagonists + κ agonists
- pentazocine
- butorphanol
- nalbuphine
-buprenorphine: weak µ agonist, κ antagonist
list the opioid antagonists
for all µ, κ, δ receptors:
- naloxone
- naltrexone
list the all clinical uses for Opioids
-analgesia
- anesthesia adjunct
- cough — anti-tussive
- diarrhea — causes constipation
- acute pulmonary edema (morphine- dec preload/afterload —> inc risk respiratory depression)
Opioid AEs:
- (1) common
- (2) less common
1- n/v, sedation, pruritus, constipation
2- urinary retention, hypotension, respiratory
______ are the only opioid effects that do not decrease in severity or disappear with prolonged use and drug tolerance
- constipation
- miosis
list the contraindications of Opioids with brief explanations
- Pregnancy: opioid withdrawal in fetus
- Head Injury: inc ICP (from injury) + hypoventilation (from opioid) –> inc CO2 –> vasodilation –> worse inc in ICP –> death
- Liver dysfunction: poor drug metabolism
- Renal dysfunction: poor clearance
- Pulmonary: not used in asthma and COPD –> higher risk of respiratory depression