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Neurology-Week 4 & 5 > Drugs-Opioids > Flashcards

Drugs-Opioids Flashcards

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1
Q

4 steps of pain

  • Understand them!
A
  1. Transduction/conduction
  2. Transmission (to CNS)
  3. Modulation
  4. Perception
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2
Q

______ pathways transmit the pain signal to the brain, and ______ pathways modulate/inhibit the pain signal

A

Ascending; Descending

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3
Q

Ascending pathway and descending pathway intersect in

A

dorsal horn of spinal cord

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4
Q

ENDOGENOUS mu opioid agonist

A

Endorphins

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5
Q

MOR are found in both the _____ and _____, but opioids produce analgesia primarily by agonizing receptors in _____.

A

CNS; PNS; CNS (brain & spinal cord)

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6
Q

Toxicities from opioid activation of MORs in the brain/spinal cord

A

Sedation

Respiratory Depression

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7
Q

Toxicities from opioid activation of MORs in the GI tract (myenteric plexus, submucosal plexus)

A

OIC (opioid-induced constipation)

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8
Q

Examples of “full” MOR agonists

A 
Codeine
Morphine
Hydrocodone
Oxycodone
Heroin

Methadone

Meperidine
Fentanyl
Remifentanil
Carfentanil

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9
Q

Examples of “partial” MOR agonists

A

Buprenorphine
Nalbuphine
Tramadol
Butorphanol

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10
Q

Examples of “neutral” MOR antagonists.

  • They inhibit the effects of opioids through competition for receptor binding.
A

Methylnaltrexone

Pentazocine

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11
Q

Examples of “inverse” MOR agonists.

  • In addition to being receptor antagonists, they inhibit the basal, opioid-independent activity of the receptors
A

Naltrexone

Naloxone

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12
Q

The potency of morphine is set to a value of

A

1

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13
Q

The higher the potency of opioid drugs, the more likely to ______

A

overdose

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14
Q

Oral administration of opioids are subject to what pharmacokinetic problem that varies based on patient’s overall liver fx and polymorphism of drug metabolizing enzyme?

A

First-pass effect

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15
Q

Most opioids are metabolized (via phase I/Phase II pathways) into polar ________ metabolites which are eliminated by the kidneys

A

Glucuronidated

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16
Q

Some opioids are metabolized into MORE potent drugs through what enzyme?

A

CYP2D6

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17
Q

Codeine, Hydrocodone, and Oxycodone can be converted through CYP2D6-mediated reactions into

A

Morphine, Hydromorphone, and Oxymorphone

  • All has morph in the name
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18
Q

Glucuronidated metabolites can have effects of their own.

The glucuronidated metabolites that have more potent analgesic effects than do the parent molecules are….

A

Morphine-6-glucuronide
Codeine-6-glucuronide

  • Notice “6” in the name
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19
Q

Glucuronidated metabolites can have effects of their own.

The glucuronidated metabolites that promote seizures and neurotoxicity, respectively, are….

A

Morphine-3-glucuronide
Hydromorphone-3-glucuronide

  • Notice “3” in the name
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20
Q

What opioid drug has a rapid time of onset and a short duration of action making it useful as an IV-opioid for general anesthesia but a poor analgesic?

A

Remifentanil

21
Q

Opioid drugs that act as analgesics exert their effects at what ascending pathway site?

A

Nociceptor neuron synaptic site in the DORSAL horn of the spinal cord

22
Q

MORs are what type of receptors?

A

GPCR

23
Q

Describe the MOA of opioids on the PRESYNAPTIC neuron of ascending pathway

A

Opioid-activated MORs inhibit the opening of Ca+2 channels during depolarization –> reduce Ca+2 influx –> slow the release of NT (glutamate)

24
Q

Describe the MOA of opioids on the POST-SYNAPTIC neuron of ascending pathway

A

Opioid-activated MORs promote opening of K+ channels –> increase K+ efflux –> hyperpolarization –> increase in depolarization threshold

25
Q

The effect of opioids on both presynaptic and post-synaptic neurons of ascending pathway is

A

to inhibit transmission of the ASCENDING pain signal and induce analgesia

26
Q

Opioid drugs that act as analgesics exert their effects at what descending pathway site?

A

Synapses in the cortex and brainstem

27
Q

Describe the MOA of opioids on the PRESYNAPTIC neuron of descending pathway

A

Opioid-activated MORs inhibit the opening of Ca+2 channels during depolarization –> reduce Ca+2 influx –> slow the release of NT (GABA) –> modulatory pain pathway is disinhibited (contributes to analgesic effect of opioids)

28
Q

What are the three toxicities associated with ACUTE opioid use

A

Sedation
Respiratory depression
Constipation

29
Q

Describe MOA of opioids in causing respiratory depression

A

Opioids can agonize MORs in respiratory control centers of the pons and medulla –> reduce signaling to diaphragm and intercostal muscles –> slow the rate of breathing

30
Q

Describe MOA of opioids in causing sedation

A

Opioids can agonize MORs in other regions of brain –> produce sedation and unconsciousness

31
Q

Describe MOA of opioids in causing OIC

A

Opioids can agonize MORs in myenteric and submucosal plexi in the GI tract –> reduce GI smooth muscle contraction –> constipation

32
Q

B/c of its constipation side effect, opioids can have therapeutic benefits in treating patients with

A

diarrhea

  • Eluxadoline (indicated tx for IBS-D)
33
Q

What MOR antagonist is considered a PAMORA and therefore can treat OIC?

A

Methylnatrexone

34
Q

What are the three toxicities associated with CHRONIC opioid use

A

Hyperalgesia (increased sensitivity to noxious stimuli)
Tolerance, dependence
Withdrawal effects

35
Q

Describe hyperalgesia caused by chronic use of opioids

A

Previously innocuous stimuli become painful –> painful stimuli become more painful

36
Q

Describe tolerance/dependence caused by chronic use of opioids

A

Extended exposure of the MORs to drug –> inactivates the MORs –> greater drug doses to produce the same analgesic effect

37
Q

The phenomenon in which tolerance to one opioid often produce tolerance to others even if the patient has not been exposed to them

A

Cross tolerance

38
Q

Tolerance to an opioid after chronic use may be addressed by switching to a different opioid; limited by cross-tolerance

A

Opioid rotation

39
Q

Describe psychological addiction caused by chronic use of opioids

A

Opioids stimulate mesolimbic dopaminergic pathway (VTA to nucleus accumbens) –> produce euphoria –> addiction

40
Q

Describe opioid withdrawal caused by chronic use of opioids

A

Physical & psychological symptoms begin within HOURS of taking the last dose –> body aches, chills, muscle pain, diarrhea, dilated pupils, anxiety –> peak symptoms begin to subside within 3-4 DAYS –> symptoms linger for weeks and months

41
Q

What opioid drug is used to reduce withdrawal symptoms and ease detoxification b/c of its long biological half-life and duration of action?

A

Methadone (“full agonist”)

42
Q

What opioid drug is given after withdrawal symptoms begin b/c of its high potency/affinity?

A

Buprenorphine (“partial agonist”)

43
Q

What opioid drugs are used to treat acute opioid overdoses?

A

Naltrexone

Naloxone

44
Q

How are Naltrexone and Naloxone administered b/c of its low ORAL bioavailability?

A

Naltrexone (IM)

Naloxone (nasal)

45
Q

What opioid drug is a combination of Buprenorphine + Naloxone to treat opioid use disorder?

A

Suboxone (sublingual)

46
Q

What is the REAL role of naloxone in Suboxone?

A

Naloxone prevents the abuse of buprenorphine

  • Naloxone doesn’t cross sublingual epithelium so it has no direct therapeutic effect in Suboxone.
47
Q

Cardiac/behavioral/GI/antibiotic drugs are CYP3A4/2D6 (inducers/inhibitors); slow the metabolic conversion of parent drugs and increase toxicities

A

inhibitors

48
Q

anticonvulsant/anti-inflammatories/behavioral drugs are CYP3A4/2D6 (inducers/inhibitors); increase the metabolic conversion of parents drugs; the metabolites can become more potent than the parent drugs leading to new toxicities

A

inducers

Neurology-Week 4 & 5 (14 decks)

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