Opioid Narcotic Analesics And Related (Fitz) Flashcards

1
Q

List generic names of soluble, bioavailable, opioid narcotic agonists used for analgesia/other indications

A
Codeine
Fentanyl
Heroin
Hydrocodone
Hydromorphone
Meperidine
Methadone
Morphine
Oxycodone
Oxymorphone
Tramadol
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2
Q

List generic names for opioid narcotic mu receptor antagonists used for management of opioid narcotic overdose/addiction/side effects

A

Naloxone
Naltrexone
Methyl naltrexone (GI specific)

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3
Q

List generic names of opioid partial agonists or mixed agonists/antagonists

A

Buprenorphine
Buprenorphine-naloxone
Pentazocine

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4
Q

List generic names of insoluble, poorly absorbed opioid receptor agonists used for diarrhea

A

Loperamide

Diphenoxylate

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5
Q

List generic names of most common opioid related anti-tussive agents (cough suppression)

A

Codeine
Dextromethorphan
Hydrocodone

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6
Q

What are the types of opioid receptors and their physiological ligands?

A

Ligands are peptides

Mu MOR: endorphins
Kappa KOR: dynorphins
Delta DOR: enkephalins, endorphins

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7
Q

Where are the opioid sites of action in the CNS/PNS?

A

Cortex and limbic system: thalamus and hypothalamus
Midbrain: periaqueductal gray
Medulla: reticular formation, locus ceruleus, raphe nuclei
Spinal cord: spinothalamic (mescencephalic, reticular tracts)

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8
Q

Describe the pain impulse at pre and post synaptic neurons. Describe opioid agonist-mediated signaling

A

Opioid receptors unoccupied

  1. Afferent sensory signal
  2. Increases Ca2+ influx (presynaptic)
  3. Increases glutamate discharge (presynaptic)
  4. Increases NMDA receptor-Na+ influx (postsynaptic)

Opioid agonist occupies opioid receptors

  1. Blunts afferent signal
  2. Blunts Ca2+ influx
  3. Blunts glutamate discharge
  4. Increases K+ efflux
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9
Q

Of the drugs that bind to mu opioid receptors, which are full agonists, partial agonists, and antagonists?

A

Full agonists:
Fentanyl
Morphine

Partial agonist/mixed
Buprenorphine

Mu/kappa mixed:
Pentazocine

Antagonist
Naloxone
Naltrexone

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10
Q

In detail, describe opioid binding and receptors

A

Opioids bind to G-protein-linked membrane receptors: mu, kappa, delta. Subtypes, splice variants confer diversity

Receptors are widely distributed throughout human body, including brain, spinal cord, gut, uterus, etc. Majority of clinically useful opioid analgesic drugs have significant agonist activity at mu receptors

Opioid receptors bind endogenous peptides and drugs

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11
Q

Describe the pain treatment ladder based on opioid-sparing rationale

A

Mild pain:
-NSAID, acetaminophen

Moderate/persisting/uncontrolled:

  • Codeine
  • Codeine-related +/- acetaminophen
  • tramadol

Severe/persisting/uncontrolled:

  • Morphine
  • Fentanyl
  • extended release forms
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12
Q

List analgesic mechs and clinical utility

A

Acetaminophen,NSAIDS
COX-1,-2
Tissue injury»acute or nerve injury

Opioids, prototype morphine
Mu receptor agonists
Tissue injury=acute stimuli>nerve injury

Anticonvulsant (gabapentin)
Ca2+ channel antagonists
Nerve injury>tissue injury=acute

Antidepressants (amitryptilene)
Reuptake inhibitor
Nerve injury>tissue injury»acute stimuli

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13
Q

What is the prototype mu agonist?

A

Morphine

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14
Q

Describe clinical effects of agonists acting on mu receptor MOR

A
Analgesia (supra-spinal)
Euphoria
CNS and respiratory depression
Drug dependence
Miosis (pupil contraction)
GI, uterine motility
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15
Q

Describe clinical effects of agonists acting on kappa receptor KOR

A

Analgesia (spinal)
Sedation
Miosis
GI, uterine motility

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16
Q

Describe tolerance to morphine (mu agonist)

A

Tolerance: over time, for a given dose, response deteriorates, necessitating increase in dose or rotation to different opioid
-analgesia, euphoria, sedation, nausea, respiratory depression

No tolerance to
-miosis, constipation

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17
Q

Patient was recovering from surgery in post-anesthesia care unit (PACU). He had been receiving morphine IV for 2 hr for postsurgical pain. His resp rate was 7 per minute with shallow breaths. He did not respond to any stimuli

pH=7.15 (normal 7.4)
HCO3=22 (normal 24)
PaCO2=68 (normal 40).

Describe what happens with opioid and respiratory depression

A
  1. At baseline, pH7.4=normal
  2. Hypoventilation. Lungs retain CO2=retain acid
    - CO2 contributes to H+ to blood
  3. Rise in PaCO2=rise in H+
    PH=7.15

Increase in CO2 + H2O H2CO3 Increase in H+ + HCO3

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18
Q

Describe morphine-induced respiration depression. Contraindciations to morphine?

A

Morphine (mu agonist) depress sensitivity to CO2
Dose-related drop of respiration rate (3-4/minute in severe toxicity), minute volume, tidal exchange

Contraindications:

  • Brain injury
  • Emphysema
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19
Q

What are clinical indications for morphine?

A

Post-operative pain
-procedures and surgery

Cancer pain
-primary and metastatic malignancy

Other pain
-Sickle cell crisis, trauma, severe diarrhea, dyspnea caused by pulmonary edema from left ventricular failure

20
Q

What are the group 1 mu agonist opioid drugs?

A

Full agonists
Parenteral and oral

*Morphine
Methadone
Meperidine

Hydromorphone
Oxymorphone
Levorphanol

21
Q

What are the group 2 mu agonist opioid drugs?

A

Full agonists
Short acting

*Fentanyl
Sufentanil
Remifentanyl

22
Q

What are the group 3 mu agonist opioid drugs?

A

*Codeine-related
Hydrocodone
Oxycodone

23
Q

In group 1, potency and bioavailability are important when switching from parenteral to oral dosing or rotating between opioids. They also dictate some of the clinical uses of these drugs.

Compare and contrast their equivalent dose and oral/parenteral potency ratios

A
Morphine: 10 mg dose and Low oral/parenteral potency ratio
Methadone: 10 and high
Meperidine: 60 and medium
Hydromorphone: 1.5 and low
Oxymorphone: 1.5 and low
Levorphanol: 2-3 and high

Meperidine, hydromorphone, oxymorphone, and levorphanol differ from morphine in efficacy

Methadone and levorphanol have good oral bioavailability

24
Q

Parenteral (IV, IM, SC, Patch, buccal) opioids have high bioavailability.
Oral morphine. First-pass metabolism. Poor bioavailability. Describe morphine’s metabolism breakdown

A

Morphine->UGT 1A1, UGT 2B7-> M-3-glucuronide, M-6-glucuronide (active metabolites)

Morphine->dehydrogenase->hydromorphone (active)

Morphine->CYP3A4->Normophine (inactive)

25
Describe characteristics of methadone
Mu agonist (full agonist) Longer half-life (27 hrs vs morphine's 2 hrs) Better oral absorption/bioavailability (90% vs 20% morphine) *Useful for withdrawal/maintenance and detoxification*
26
Describe cardiac effect of methadone
Can affect cardiac electrical conduction, *producing QT-interval prolongation in acute overdose or during long-term methadone treatment* This effect is *unrelated* to its interaction with mu receptors It delays cardiac repolarization by blocking flow of K+ ions through HERG channels (K+ channels)
27
Describe meperidine distinctions as mu agonist
Eye: pupil dilation (mydriasis) Abuse difficult to detect via pinpoint pupils Accordingly, those who abuse this drug can escape detection Normeperidine, a toxic metabolite, accumulates and causes seizures
28
Describe group 2 mu agonists: short acting, high potency, full agonists
Sufentanil: kappa, delta, and mu agonists Fentanyl, sufentanil, alfentanil, remifentanil are 100x more potent than morphine, methadone Remifentanil: very short-acting
29
Describe remifentanil popularity
Group 2 mu, short acting, full agonist Gaining popularity for analgesia for childbirth if regional analgesia is either contraindicated or not desired It is metabolized by plasma and tissue esterases Although it transfers across placenta, its rapid metabolism in fetus lowers risk for neonatal depression Its rapid onset of action, within 1 minute following intravenous injection, is another advantage
30
Describe fentanyl: anesthesia and breakthrough pain
``` Strong group 2 mu agonist (meperidine analog) Used in anesthesia *Rapid onset & distribution (lipophilic) *Short duration of action (procedures) *Transmucosal (lollipop) Breakthrough pain (with morphine) *Transdermal patch delivery Slows onset and prolongs delvery ``` Caution: respiratory depression *Abuse potential via heating patches
31
Describe codeine; moderate pain & cough
As a partial agonist at mu receptors, codeine has less potential for drug dependence & respiratory depression Reliable oral absorption/bioavailability (50% vs 20% morphine) *Analgesia - moderate pain Some formulations contain acetaminophen *Anti-tussive: cough relief (*mu-independent)
32
What drug is a safer antitussive agent than codeine?
Dextromethophan It relieves cough independently of opioid receptors Not analgesic Not addictive
33
Why has codeine for pain relief following a tonsillectomy and/or adenoidectomy caused death in children with obstructive sleep apnea?
Codeine->CYP2D6->morphine Ultrafast metabolizer: CYP2D6 gene duplication & ultrafast allele -leads to life-threatening or fatal amounts morphine in body Intermediate metabolizer: CYP2D6 heterozygous Poor metabolizer: CYP2D6 gene deletion & slow allele
34
List drugs and their active metabolites
``` Morphine: M6G and M3G, hydropmorphone Heroin: Morphine Codeine: Morphine Oxycodone: oxymorphone Meperidien: normeperidine (toxic) Hydromorphone: None Oxymorphone: None Fentanyl: none ```
35
Describe opioids and the gut
Loperamide Diphenoxylate Anti-diarrheals Interact with mu opioid receptors in gut Poor solubility (limited risk of parenteral abuse) Poor penetration of BBB (limited risk of dependence/toxicity)
36
Describe tramadol
*Moderate mu agonist N-desmethyl active metabolite Reliable oral absorption/bioavailabilty (70% vs 20% for morphine) *Analgesia: moderate pain *Inhibits catecholamine reuptake Caution in patients in tricyclic or SRI anti-depressants *Associated with seizures
37
Describe pentazocine
Mixed: kappa agonist plus mu partial agonist and delta antagonist Supra-spinal analgesia Can precipitate withdrawal (in abusers) Side effects: tachycardia, hallucinations
38
Describe buprenorphine
Partial/mixed Mu partial agonist plus kappa & delta antagonist Analgesia Can precipitate withdrawal (in abusers) *office-based detox/maintenance in combination with naloxone
39
Describe heroin (illegal substance)
Di-acetylmorphine | Penetrates BBB rapidly->exaggerated euphoria->addiction liability
40
Describe addiction program compliance: % retention - 1 year
Methadone maintenance: 50-80% Buprenorphine-naloxone: 40-50% Naltrexone Maintenance: 10-20% "Drug free": 5-20%
41
What are signs of opioid analgesic overdose?
Respiratory rate
42
Describe mu receptor antagonists
``` Occupy but do not activate mu receptors Competitively inhibit (displace) heroin, morphine, fentanyl, etc (other mu agonists) from mu receptors *Antidote for opioid overdose ```
43
Describe naloxone
Can reverse coma and respiratory depression ~1 min after IV bolus Depends on what opioid and what dose Initial .04mg. If no response, then incremets to 15 mg Short duration of action 1-2 hrs can lead to apparent relapse of overdose symtpoms Antidotes for overdose can precipitate withdrawal
44
Describe naltrexone
Has a long duration of action (48 hrs for single dose orally) in overdose
45
Opioids increase smooth-muscle tone and inhibit coordinated peristalsis required for propulsion, which contributes to nausea and vomiting as well as constipation. What strategies might work for opioid-induced side effects as constipation?
Methylnaltrexone
46
What is methylnaltrexone?
Quaternary derivative of naltrexone with restricted ability to cross BBB It functions as a peripheral acting opioid antagonist, including actions on GI tract to inhibit opioid-induced decreased GI motility and delay in GI transit time, thereby decreasing opioid-induced constipation Does not affect opioid analgesic effects or induce opioid withdrawal symptoms