L40- Opioids Flashcards

1
Q

list the endogenous opioids and their source

A

source- POMC (Proopiomelanocortin)

  • endorphins
  • enkephalins
  • dynorphins
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2
Q

(1) are the clinically relevant opioid receptors, with (2) signaling and (3) as the end result

A

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)

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3
Q

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
A
1- µ, κ, δ
2- µ, κ
3- κ
4- µ
5- µ
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4
Q

list the all the CNS effects of opioid (therapeutic and adverse)

A

-analgesia

  • sedation (µ, κ)
  • euphoria
  • respiratory depression (µ)
  • cough suppression // anti-tussive
  • n/v
  • miosis (µ, κ)
  • truncal rigidity
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5
Q

list all the PNS effects of opioids (therapeutic and adverse)

A
  • hypotension
  • constipation
  • pruritus (via Histamine release)
  • contraction of biliary smooth muscle – contraindicated with biliary colic
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6
Q

Opioids:

  • (activates/inhibits) ascending pain pathway
  • (activates/inhibits) descending pain pathway
A

1- inhibits

2- activates (serotonergic, adrenergic)

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7
Q

describe opioid effect on ascending pain pathway

A

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

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8
Q

describe the normal functions of descending pain pathway and then how opioids change this pathway

A
  • 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

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9
Q

list the opioid agonists (not mixed):

  • indicate most potent
  • indicate least potent
A
  • *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
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10
Q

list the mixed opioid agonists (describe general activity)

A

µ antagonists + κ agonists

  • pentazocine
  • butorphanol
  • nalbuphine

-buprenorphine: weak µ agonist, κ antagonist

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11
Q

list the opioid antagonists

A

for all µ, κ, δ receptors:

  • naloxone
  • naltrexone
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12
Q

list the all clinical uses for Opioids

A

-analgesia

  • anesthesia adjunct
  • cough — anti-tussive
  • diarrhea — causes constipation
  • acute pulmonary edema (morphine- dec preload/afterload —> inc risk respiratory depression)
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13
Q

Opioid AEs:

  • (1) common
  • (2) less common
A

1- n/v, sedation, pruritus, constipation

2- urinary retention, hypotension, respiratory

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14
Q

______ are the only opioid effects that do not decrease in severity or disappear with prolonged use and drug tolerance

A
  • constipation

- miosis

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15
Q

list the contraindications of Opioids with brief explanations

A
  • 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
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16
Q

list and explain the 2 main concerning drug interactions with opioids

A

1) Sedatives/Hypnotics => dec CNS and dec respirations

2) Serotonin Syndrome with MAOIs:
- delirium, hyper/hypo-tension, coma, death
- convulsions, HA, rigidity, hyperthermia

17
Q

list the opioids that have the biggest risk for serotonin syndrome

A
  • levophanol
  • methadone
  • meperidine
  • tramadol
  • fentanyl
18
Q

______ is the drug of choice for severe pain, include receptor activity

A

Morphine, Hydromorphone, Oxymorphone:

  • µ agonist, high affinity
  • κ, δ agonist, low affinity
19
Q

describe morphine metabolism

A

Morphine –>

  • M3G
  • M6G (10%): more potent, but no analgesic effects
  • Normorphine –> Normorphine glucoronide

Note- none can cross BBB

20
Q

describe Heroin effects and metabolism

A

Heroin (diacetylmorphine) –> rapidly hydrolyzed into 6-MAM (monoacetylmorphine) –> hydrolized into morphine

  • 6-DAM, 6-MAM are more liposoluble than morphine –> crosses BBB
  • 6-MAM, morphine are responsible for analgesia
21
Q

Meperidine:

  • (1) receptor activity
  • (2) clinical use
  • (3) AEs
A

1- µ agonist only
2- short-term pain

3- Metabolite (normeperidine) causes toxicity (worse in CKD) => hallucinations, muscle twitches, tremors, seizures

22
Q

______ is an opioid that causes hallucinations, muscle twitches, tremors, seizures (worse in CKD)

A

Meperidine (3hr 1/2 life) –> Normeperidine toxic metabolite (20hr 1/2 life)

23
Q

Fentanyl:

  • (1) receptor activity
  • (2) clinical use
  • (3) describe unique pharmacokinetics
A

1- µ agonist only
2- severe acute pain

3:

  • rapid onset –> short duration (15-30 mins)
  • 100x more potent than morphine
24
Q

Methadone:

  • (1) receptor activity (hint- more than one)
  • (2) clinical use
  • (3) describe unique pharmacokinetics
  • (4) important AE
A

1:

  • µ agonist only
  • NMDA antagonist
  • SERT and NET inhibition

2:

  • chronic pain
  • opioid withdrawal Tx

3:

  • longer duration / longer 1/2 life –> maintains constant levels
  • less euphoria and sedation

4- QT prolongation / Torsades de pointes

25
Q

Levorphanol:

  • (1) receptor activity (hint- more than one)
  • (2) clinical use
  • (3) AE
A

1:

  • µ, κ, δ agonist
  • NMDA antagonist
  • SERT and NET inhibitors

2- severe pain

3- less n/v than morphine

26
Q

______ opioids have NMDA antagonist activity and SERT/NET inhibitor activity

A
  • methadone

- levorphanol

27
Q

(Oxy/Hydro)-codone is only available in combination with (2) and they are used to treat (3)

A

1- hydrocodone
2- acetaminophen / NSAID
3- moderate to severe pain

Oxycodone can be alone or in combination

28
Q

Codeine:

  • (1) receptor activity
  • (2) clinical use
  • (3) contraindication, explain
A

1- weak µ, δ agonists

2- mild to moderate pain

3- children: more rapid CYP2D6 metabolizers –> ineffective

29
Q

list mixed opioid agonists and describe their clinical uses / effects

A

all can be used for Pain: opioid-naive Pts (no previous use) –> use is limited due to Ceiling Effect

1) Pentazocine, Nalbuphine, Butorphanol (µ agonist, κ antagonist) —> Psychotomimetric Effect
2) Buprenorphine (µ antagonist, κ agonist) –> opioid withdrawal

30
Q

list the opioid antagonists and describe their clinical uses

A

Naloxone- acute opioid overdose

Naltrexone- opioid and alcohol addiction (reduces cravings via DA pathway)

31
Q

Tramadol:

  • (1) receptor activity
  • (2) clinical uses
  • (3) AEs
  • (4) contraindication
A

1:

  • µ agonist
  • SERT, NET inhibitor

2- moderate pain and chronic neuropathic pain

3- seizures, serotonin syndrome
4- children

32
Q

(1) is a common anti-tussive that can be combined with (2) opioid. (3)- describe actions of (1).

A

Dextromethorphan: lower dose needed than for pain, no opioid receptor activity
-acts centrally to inc threshold for coughing

-paired with Codeine

33
Q

______ are a common anti-diarrheal agents that act on opioid receptors

A

Diphenoxylate-Atropine

Loperamide