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

Drugs-Opioids Flashcards

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?

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
The effect of opioids on both presynaptic and post-synaptic neurons of ascending pathway is
to inhibit transmission of the ASCENDING pain signal and induce analgesia
26
Opioid drugs that act as analgesics exert their effects at what descending pathway site?
Synapses in the cortex and brainstem
27
Describe the MOA of opioids on the PRESYNAPTIC neuron of descending pathway
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
What are the three toxicities associated with ACUTE opioid use
Sedation Respiratory depression Constipation
29
Describe MOA of opioids in causing respiratory depression
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
Describe MOA of opioids in causing sedation
Opioids can agonize MORs in other regions of brain --> produce sedation and unconsciousness
31
Describe MOA of opioids in causing OIC
Opioids can agonize MORs in myenteric and submucosal plexi in the GI tract --> reduce GI smooth muscle contraction --> constipation
32
B/c of its constipation side effect, opioids can have therapeutic benefits in treating patients with
diarrhea * Eluxadoline (indicated tx for IBS-D)
33
What MOR antagonist is considered a PAMORA and therefore can treat OIC?
Methylnatrexone
34
What are the three toxicities associated with CHRONIC opioid use
Hyperalgesia (increased sensitivity to noxious stimuli) Tolerance, dependence Withdrawal effects
35
Describe hyperalgesia caused by chronic use of opioids
Previously innocuous stimuli become painful --> painful stimuli become more painful
36
Describe tolerance/dependence caused by chronic use of opioids
Extended exposure of the MORs to drug --> inactivates the MORs --> greater drug doses to produce the same analgesic effect
37
The phenomenon in which tolerance to one opioid often produce tolerance to others even if the patient has not been exposed to them
Cross tolerance
38
Tolerance to an opioid after chronic use may be addressed by switching to a different opioid; limited by cross-tolerance
Opioid rotation
39
Describe psychological addiction caused by chronic use of opioids
Opioids stimulate mesolimbic dopaminergic pathway (VTA to nucleus accumbens) --> produce euphoria --> addiction
40
Describe opioid withdrawal caused by chronic use of opioids
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
What opioid drug is used to reduce withdrawal symptoms and ease detoxification b/c of its long biological half-life and duration of action?
Methadone ("full agonist")
42
What opioid drug is given after withdrawal symptoms begin b/c of its high potency/affinity?
Buprenorphine ("partial agonist")
43
What opioid drugs are used to treat acute opioid overdoses?
Naltrexone | Naloxone
44
How are Naltrexone and Naloxone administered b/c of its low ORAL bioavailability?
Naltrexone (IM) | Naloxone (nasal)
45
What opioid drug is a combination of Buprenorphine + Naloxone to treat opioid use disorder?
Suboxone (sublingual)
46
What is the REAL role of naloxone in Suboxone?
Naloxone prevents the abuse of buprenorphine * Naloxone doesn't cross sublingual epithelium so it has no direct therapeutic effect in Suboxone.
47
Cardiac/behavioral/GI/antibiotic drugs are CYP3A4/2D6 (inducers/inhibitors); slow the metabolic conversion of parent drugs and increase toxicities
inhibitors
48
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
inducers

Neurology-Week 4 & 5 (14 decks)

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