Lecture 14: Narcotic Analgesics Flashcards Preview

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Flashcards in Lecture 14: Narcotic Analgesics Deck (38)
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1
Q

Which opioid agonist is used for pulmonary edema?

A

Morphine

2
Q

Which 2 opioid agonists are used for severe pain and as an adjunct in anesthesia?

A
  • Fentanyl
  • Morphine
3
Q

What is the MOA on both the presynaptic μ-receptor and post-synaptic μ-receptor by opioids?

A
  • Presynaptic μ-receptor activation INHIBITS Ca2+ influx into sensory neurons, which decreases NT release
  • Post-synaptic μ-receptor activation INCREASES K+ efflux, which decreases postsynaptic response to excitatory neurotransmission
4
Q

What are the 3 opioids which are strong μ-receptor agonists?

A
  1. Morphine
  2. Fentanyl
  3. Methodone
5
Q

What are the pharmacokinetics of the strong opioid agoinsts?

Exception?

A
  • First pass effect
  • Duration 1-4 hours
  • Except methadone = 4-6 hours
6
Q

What’s the MOA of Codeine and Hydrocodone, as compared to the strong opioid agonists?

A
  • Less efficaious than morphine, partial μ-receptor agonists
  • Can antagonize strong agonist
7
Q

What are the clinical applications of Codeine and Hydrocodone?

A
  • Mild-moderate pain
  • Cough (codeine)
8
Q

What are the 2 opioids belonging to the class of mixed opioid agonist-antagonist?

A
  • Buprenorphine
  • Nalbuphine
9
Q

What are effects of the opioids, Buprenorphine and Nalbuphine?

A
  • Like strong agonists, but can antagonize their effects
  • Also reduces craving for alcohol
10
Q

What is Buprenorphine used for clinically?

A
  • Moderate pain
  • Some maintenane rehabilitation programs
11
Q

What is the duration of action for Buprenorphine and Nalbuphine and associated toxicity?

A
  • Long duration of action: 4-8 hours
  • May precipitate abstinence syndrome
12
Q

What is the clinical application for the use of the opioid, Nalbuphine?

A

Moderate pain

13
Q

What is the effect of Dextromethorphan?

A
  • Reduces cough reflex
  • Not an analgesic
14
Q

What is Dextromethorphan used for?

A

Acute debilitating cough

*This is Nyquil or Robitussin = Antitussives

15
Q

What is the MOA of Naloxone?

A

Strong antagonist of μ, δ, and k receptors

16
Q

What is clinical application for Naloxone?

A

Opioid overdose

17
Q

What is a potential toxicity associated with Naloxone?

A

Precipitates abstinence (withdrawl) syndrome in dependent users

18
Q

What is the MOA of Naltrexone and Nalmefene; how are they different from Naloxone?

A
  • Strong antagonist of μ, δ and k receptors (just like Naloxone)
  • Longer duration of action (10 hours!)
19
Q

What are some of the clinical applications of Naltrexone?

A
  • Maintenance programs and can block heroin effects for up to 48 h
  • Used for alcohol and nicotine dependence

*When combined with bupropion may be effective in weight-loss programs

20
Q

What are the functions/downstream effects caused by activation of the μ-receptor?

A
  • Supraspinal and spinal analgesia
  • Sedation
  • Inhibition of respiration
  • Slowed GI transit
  • Modulation of hormone and NT release
21
Q

What are the functions/downstream effects caused by activation of the δ-receptor?

A
  • Supraspinal and spinal analgesias
  • Modulation of hormone and NT release
22
Q

What are the functions/downstream effects caused by activation of the k-receptor?

A
  • Supraspinal and spinal analgesias
  • Psychotomimetic effects
  • Slowed GI transit
23
Q

What is the endogenous opioid peptide affinity for μ, δ, and k-receptor (endorphins, dynorphins, and enkephalins?

A
  • μ-receptor: Endorphins > enkephalins > dynorphins
  • δ-receptor: Enkephalins > endorphins and dynorphins
  • k-receptor: Dynorphins >> endorphins and enkephalins
24
Q

What is the MOA of Nalbuphine?

A
  • k-receptor agonist
  • μ-receptor antagonist

*Mixed opioid agonist-antagonist

25
Q

What is the MOA of Buprenorphine?

A
  • Partial/weak μ-receptor agonist
  • k-receptor antagonist

*Mixed opioid agonist-antagonist

26
Q

Which 5 opioids are partial or weak agonists of μ-receptors?

A
  • Hydrocodone
  • Codeine
  • Pentazocine
  • Buprenorphine
  • Butorphanol
27
Q

Which opioid is a strong k-receptor agonist and partial/weak agonist of μ-receptors; and can only be given parenterally?

A

Butorphanol

28
Q

What are some of the adverse effects associated w/ acute use of opioids?

A
  • Respiratory depression
  • Nausea/vomiting
  • Pruritus/Uticaria
  • Constipation and Urinary retention
  • Delirium – Sedation
  • Myoclonus
  • Seizures
29
Q

What are some of the adverse effects associated w/ chronic use of opioids?

A
  • Hypogonadism
  • Immunosuppression
  • Increased feeding
  • Increased GH secretion
  • Withdrawl effects
  • Tolerance, dependence –> Abuse, addiction
  • Hyperalgesia (increased sensitivity to pain)
  • Imapirment while driving
30
Q

What are the relative contraindications for morphine?

A
  • Acute respiratory depression
  • Renal failure (due to accumulation of the metabolites morphine-3-glucuronide and morphine-6-glucuronide)
  • Chemical toxicity (potentially lethal in low tolerance patients)
  • Raised ICP, including head injury (risk of worsening respiratory depression)
  • Biliary colic
31
Q

How does the physiological state of obesity play a role in the pharmacokinetic variance in use of narcotic analgesics?

A
  • Overdosage
  • Central Vd is not reflected by ABW
  • Increased adipose tissue causes and increase in total Vd —> prolongs elimination half-life
32
Q

What are 2 pharmacokinetic variances in the elderly that must be accounted for when administering narcotic analgesics?

A

1) Decreased neuronal mass and decreased central Vd —> Increased sensitivity to opioids
2) Decreased LBM w/ increased adipose tissue causes increase in total Vd + Decreased Hepatic Blood Flow (by 40-50% age 75) –> Prolongs effect of infusion

33
Q

What pharmacokinetic variances in infants need to be accounted for when administering narcotic analgesics?

A

Decreased conjugation capacity and immature renal function —> Prolonged effect

34
Q

By what mechanism may renal failure lead to morphine toxicity?

A
  • Accumulation of Morphine-6-Glucuronide (M6G)
  • Possible hydrolysis of glucuronides back to parent compound
  • Uraemia potentiates CNS depression and increased BBB permeability
35
Q

Renal failure may lead to Pethidine toxicity due to the accumulation of __________

A

Norpethidine

36
Q

What is the mechanism by which severe liver failure may lead to increase sensitivity to opioids?

There may be synergism when?

Which drugs will have an increased elimination half-life?

A
  • Synergism if encephalopathic
  • Altered integrity of BBB
  • Increased elimination half-life for pethidine and tramadol
37
Q

Which 3 genes related to opioid receptors and signal transduction have been implicated as genetic factors in the Pharmacodynamics of Opioids?

A
  • OPRM1
  • COMT
  • MC1R
38
Q

Which genes related to metabolizing enzymes and transporters have been implicated in the variation of the Pharmacokinetic profile of Opioids?

A
  • CYP2D6 and UGT2B7 —> Metabolizing enzymes
  • ABCB1 —> Transporter