SM_236a, 240a: Pharmacology, Opioids, and Pain Concepts I and II Flashcards Preview

MSK/Derm > SM_236a, 240a: Pharmacology, Opioids, and Pain Concepts I and II > Flashcards

Flashcards in SM_236a, 240a: Pharmacology, Opioids, and Pain Concepts I and II Deck (43)
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1
Q

Describe the opioid receptors

A

Opioid receptors

  • Mu, kappa, delta
  • One gene codes for each
  • Subtypes come from splice variants
  • All involved in brain, spinal, GI sites
2
Q

The opioid receptors are _____, _____, and _____

A

The opioid receptors are mu, happa, and delta

3
Q

Mu opioid receptor is responsible for ____, ____, ____, ____, ____, ____, and ____

A

Mu opioid receptor is responsible for analgesia, euphoria, dependence, respiratory depression, miosis, GI effects, and pruritis

(named after morphine)

4
Q

Kappa opioid receptor is responsible for ____, ____, and ____

A

Kappa opioid receptor is responsible for mild analgesia, less respiratory depression, and pyschomimetic effects (unlike euphoria)

5
Q

Delta opioid receptor function is ____

A

Delta opioid receptor function is unknown

6
Q

Opioid receptors are found in the ____, ____, and ____

A

Opioid receptors are found in the brain, spinal cord, and gut

7
Q

Describe the location of opioid receptors in the brain

A
  • Amygdala - emotion
  • Brainstem - ventilation
  • Area postrema - vomiting
  • Periaqueductal gray - inhibitory pathway

(gate control theory, periaqueductal gray inhibits pain transmission in dorsal horn via a relay in the rostral ventral medulla)

8
Q

Opioid receptors work via ____, which ____, ____, ____, and ____

A

Opioid receptors work via G receptor proteins, which inhibit cellular adenylyl cyclase, increase K+ currents and decrease Ca2+ currents, cause hyperpolarization, and decrease nociceptive transmission

9
Q

Opioids work on ____ and ____ receptors

A

Opioids work on presynaptic and postsynaptic receptors

10
Q

Opioids activate the ____, triggering ____ and releasing ____

A

Opioids activate the periaqueductal gray, triggering the descending inhibitory pathways and releasing endorphins

(descending pathway modulates pain in transmission in the ascending pathway)

11
Q

Opioids ____ the GABA neuron, which allows for ____ of the pain inhibitory neuron

A

Opioids inhibit the GABA neuron, which allows for activation of the pain inhibitory neuron

12
Q

Opiate is a _____

A

Opiate is a drug derived from opium

13
Q

Opioid is ____

A

Opioid is all drugs, both natural and synthetic, that bind to opioid receptor

14
Q

Narcotic is ____, ____, and ____

A

Narcotic is any substance that induces sleep, acts on opioid receptors, and any illicit substance

15
Q

Opioids that are agonists are _____ and include _____, _____, and _____

A

Opioids that are agonists are mu receptor agonists and include morphine, merepiridine, and hydromorphone

16
Q

Opioids that are antagonists are _____ and include _____ and _____

A

Opioids that are antagonists are mu receptor antagonists and include naloxone and naltrexone

17
Q

Opioids that are agonist/antagonists are _____ and include _____ and _____

A

Opioids that are agonist/antagonists are kappa agonists / mu antagonists and include butorphanol and nalbuphine

18
Q

Opioids that are partial agonists are _____ and _____ and include _____

A

Opioids that are partial agonists are partial mu agonists with high affinity and meaningless kappa antagonists and include buprenoprhine

19
Q

Describe opioids that are agonist/antagonists

A

Agonist/antagonist opioids

  • Analgesia is kappa mediated
  • Weak mu receptor antagonist
  • Ceiling effect
  • Less GI side effects
  • Kappa: less respiratory depression / sedation / euphoria but makes person nuts
  • Can trigger withdrawal so do not use in opioid tolerant patient
  • Can reverse opioid side effects at low dose
20
Q

Describe opioids that are partial agonists

A

Partial agonist opioids

  • Only partial mu agonist
  • Ceiling effect for agonism
  • Binds mu with high affinity: higher than most opioids, prevents other opioids from binding, makes naloxone reversal difficult in overdose
  • Current use: opioid maintenance, not so much for chronic pain
21
Q

Partial agonist opioids are used for ____

A

Partial agonist opioids are used for opioid maintenance

22
Q

Describe neurologic effects of opioids

A

Neurologic effects of opioids

  • Analgesia: supraspinal and spinal cord level, not reliably associated with loss of consciousness, better for nociceptive pain (pain caused by stimulation of nociceptive receptors) than neuropathic pain (pain caused by damaged neural structures)
  • Miosis (pinpoint pupil): seen with all opioid agonists
  • No tolerance to this: useful in overdose diagnosis, even in tolerant addicts
23
Q

____ is the major way that opioids kill

A

Respiratory depression is the major way that opioids kill

(hold if sedated)

24
Q

Describe respiratory effects of opioids

A

Respiratory effects of opioids

  • Therapeutic effects: prevent hyperventilation from pain and anxiety, opioids can be used for their antitussive actions, can help avoid increases in bronchomotor tone in asthma
  • Adverse effect: respiratory depression is most serious, activation of mu opioid receptor in caidal medullary raphe region inhibits the ventilatory response to hypercapnia
25
Q

Direct cardiac actions are _____ than for other inhalational or IV anesthetics

A

Direct cardiac actions are lower than for other inhalational or IV anesthetics

26
Q

GI effects of opioids include ____ and ____

A

GI effects of opioids are slowed peristalsis and nausea/vomiting

  • Slowed peristalsis: via enteric NS opioid receptors
  • Nausea/vomiting: via chemoreceptor trigger zone
27
Q

Tolerance to opioids does NOT include ____ and ____

A

Tolerance to opioids does NOT include miosis and constipation

(tolerant to euphoria, sedation, analgesia, N/V, respiratory depression)

28
Q

Opioid withdrawal contains symptoms of ____

A

Opioid withdrawal contains symptoms of sympathetic overdrive

  • Anxiety, insomnia, diaphoresis, yawning, rhinorrhea, lacrimation
  • HTN, tachycardia
  • Hyperventilation
  • Mydriasis
  • Also diarrhea and abdominal cramps
29
Q

Opioid overdose symptoms include ____, ____, and ____

A

Opioid overdose symptoms include respiratory depression / arrest, sedation or unresponsiveness, and miosis

(ABCs - support ventilation, use naloxone as the antagonist)

30
Q

List the agonist, antagonist, agonist/antagonist, and partial agonist opioids

A

Opioids

  • Agonists: morphine, codeine, hydrocodone, oxycodone, merperidine, fentanyl, hydromorphone, methadone, tramadol
  • Antagonists: naloxone, naltrexone
  • Agonist/antagonist: nalbuphine
  • Partial agonist: buprenorphine
31
Q

Describe morphine

A

Morphine

  • Hydrophilic: delayed transport across BBB so delayed onset of action
  • Broken down into M3G and M6G - only M6G is active
  • Duration of action is 4-5 hours (t1/2 = 2-3 hours)
  • Causes histamine release: rash, hypotension
32
Q

Describe oxycodone

A

Oxycodone

  • Semisynthetic opioid closely related to morphine
  • High bioavailability (60%) compared to morphine (33%)
  • Analgesia is via parent compound but does metabolize into oxymorphone (often undetectable but 14x more potent)
  • Immediate release and extended release formulation
33
Q

Describe codeine

A

Codeine

  • Prodrug (very low mu affinity)
  • 10% metabolized to morpine - 7-10% of white population cannot
  • Considered a weak opioid but can get nausea and constipation from parent drug at high doses
34
Q

Describe hydrocodone

A

Hydrocodone

  • Only sold as combo drug in US: Norco or vicodin (combined with acetaminophen)
  • Breakdown into hydromorphone
  • Unknown if analgesia is via parent drug or metabolite
35
Q

Describe hydromorphone

A

Hydromorphone

  • Analogue of morphine and similar in action (hydrophilic, duration of analgesia)
  • Better side effect profile than morphine: pruritis, sedation, nausea, vomiting
  • 5x more potent orally and 7x more potent parenterally
  • Metabolized in liver to H3G: lacks analgesia, could potentiate side effects
36
Q

Describe fentanyl

A

Fentanyl

  • Highly lipophilic with high affinity for the mu receptor: fast onset IV, crosses skin and buccal tissue
  • 75-125x more potent than morphine
  • IV for OR anesthesia and ICU analgesia: fast onset, easy to titrate, short duration so good for outpatient surgeries
  • Transdermal: slow onset because builds up subcutaneously, sustained release for chronic pain, more difficult to abuse, good for patients with GI issues, variable time achieving therapeutic levels with skin differences
37
Q

Describe merperidine

A

Merperidine

  • Lipophilic with rapid onset
  • Weaker mu agonist as compared to morphine
  • Potent inhibitor of serotonin reuptake
  • Metabolite is normeperidine: long half life, CNS hyperactivity and seizures, cleared by kidneys, do NOT use in renal failure patients
38
Q

Describe tramadol

A

Tramadol

  • Oral analgesic
  • Technically a prodrug: M1 metabolite is a mu agonist
  • Works by two mechanisms: mu receptor agonist, blocks reuptake of 5-HT and NE
  • Used for mild to moderate pain
39
Q

Describe naloxone

A

Naloxone

  • Opioid antagonist: IV only
  • Short half life of 1 hour
  • Duration of 15 min - 4 hours
  • Reversal is short-lived
  • Very poor bioavailability so combined in opioid pills to prevent IV abuse
  • Competitive antagonist
40
Q

Interpatient opioid receptor variability occurs with respect to ____, ____, and ____

A

Interpatient opioid receptor variability occurs with respect to receptor type, density, and location

41
Q

Different opioids have ____ receptor affinities due to ____

A

Different opioids have different receptor affinities due to splice variants

(subtle differences between splice variant affinities)

42
Q

Describe opioid receptor relevance

A

Opioid receptor relevance

  • Interpersonal receptor density varaibility
  • Different opioids have different receptor affinities
  • Different opioids have different effects in different patients
  • Titrate opioid to analgesic effect
  • Change the opioid if side effects and not much analgesia
43
Q

____ and ____ are problematic in patients with renal failure

A

Morphine and merperidine are problematic in patients with renal failure

  • Morphine metabolites M3G and M6G cleared by kidney -> if not cleared can cause massive side effects
  • Merperidine metabolite normoperidine is cleared by kidneys -> if not cleared can cause CNS hyperactivity and seizures

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