Opioids Flashcards

1
Q

what do opioids do for level of wakeness and pain

A

General anesthetics produce unconsciousness but do not inhibit pain signal generation or propagation

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2
Q

why do patients not feel mildly painful surgical manipulations

A

Patients do not feel mildly painful surgical manipulations (e.g., a skin incision) simply because the small numbers of pain signals, which are transmitted to the Reticular Activating System (RAS) in the medulla, are insufficient to awaken the patient

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3
Q

how do we prevent the RAS from being stimulated to the point that an anesthetized patient wakes up?

A

We can prevent this by administering an analgesic beforehand to inhibit pain signal generation

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4
Q

is it safe to administer analgesic before anesthetic? why?

A

This is safer than trying to maintain unconsciousness using higher doses of general anesthetic (which inhibits respiration & CVS function in a dose dependent manner)

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5
Q

four things opioid drugs are used for

A

-analgesia; management of moderate to severe pain
-sedation
-cough suppressant (antitussive)
-treatment of diarrhea (constipation is a major side effect)

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6
Q

what three opioid receptor families mediate analgesia

A

mu (MOR)
delta (DOR)
kappa (KOR)

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7
Q

what one of the opioid receptor families produces dysphoria

A

sigma

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8
Q

what is the mechanism of opioid receptors

A

Opioids stimulate opioid receptors in pain pathways

K+ channels open which causes hyperpolarization and then inhibition of APs

also inhibition of calcium entry which inhibits NT release

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9
Q

main effect of MOR stimulation, and others

A

analgesia; full stimulation causes intense analgesia effects

-euphoria
-miosis or mydriasis
-respiratory depression

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10
Q

main effect of KOR stimulation, and others

A

analgesia; moderate effect, and primarily visceral

-negligable respiratory depressive effects

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11
Q

what opioid receptor mediated respiratory depression

A

Mu receptor

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12
Q

difference between full vs partial agonists

A

full = opioid maximally stimulates opioid receptor

partially = opioid weakly stimulates opioid receptor

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13
Q

what makes a mixed agonist/antagonist

A

some opioids are agonists at some opioid receptors and antagonists at others

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14
Q

what type of agonist is fentanyl and what effect does it have

A

Fentanyl is a full mu agonist = produces an intense analgesic
effect via MOR

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15
Q

what type of agonist is butorphenol and what effect does it have

A

Butorphanol is a kappa agonist
with mild to moderate analgesic
effect

It also very weakly stimulates Mu
receptors, acting as a competitive
antagonist to full Mu agonists

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16
Q

what is the analgesic effect of butorphenol and fentanyl combined

A

weaker analgesia than with fentanyl alone

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17
Q

primary effect of

A
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18
Q

what drugs have a mu receptor and what are their interactions

A

codeine, morphine, hydromorphone, meperidine, fentanyl (all agonists)

buprenorphine and butorphenol (partial agonist)

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19
Q

what drugs have a kappa receptor and what are their interactions

A

buprenorphine and butorphenol (full agonists

20
Q

what drugs have analgesia as their primary effect

A

codeine, morphine, hydromorphone, meperidine, fentanyl, buprenorphine and butorphenol

21
Q

what drug is good to use for cough suppression

A

butorphenol

22
Q

what drug is good to use for constipation

A

loperamide

23
Q

what drug is good to use for emesis in dogs

A

apomorphine

24
Q

what is the relative duration of analgesia for buprenorphine

A

4-8 hours

25
Q

what is the relative duration of analgesia for hydromorphone

A

3-6 hours

26
Q

what is the analgesic potentcy of fentanyl relative to morphine

A

100x

27
Q

how are opioids normally administered and why

A

Phase I & Phase II metabolism with high first-pass effect = most opioids are therefore administered parenterally

28
Q

do dogs convert codeine into morphine

A

only at low or negligable amounts. not nearly the same as humans do

29
Q

what can high doses of morphine cause?

A

excitement
-sham rage (cats)
-typically not seen with hydromorphone

30
Q

physiological effects of full Mu agonists on the CNS

A

-3-6 hours of sedation/analgesia
-sedation is most likely in dogs, excitement is most likely in other species

31
Q

physiological effects of full Mu agonists on the cardiovascular system

A

Usually little effect on CVS at the dosages normally administered

32
Q

what can morphine trigger

A

may trigger histamine release = vasodilation = hypotension

33
Q

physiological effects of full Mu agonists on the respiratory system

A
  • Dose-dependent depression
  • More intense effect when combined with a general anesthetic
  • Death from overdose is due to respiratory arrest – a Mu effect
  • Use naloxone to reverse
  • Opioids suppress the cough reflex
34
Q

physiological effects of full Mu agonists on the gastrointestinal system

A
  • Increase segmentation but reduce propulsion in large bowel = stool becomes dehydrated = constipation
  • Bile duct sphincter constriction = increase in gall bladder pressure
    = biliary colic
  • Nausea & vomiting (chemoreceptor trigger zone MOR stimulation)
35
Q

what do opioids do to the bladder

A

Urinary bladder sphincter tone increased & detrusor muscle tone
increased = urgency to urinate but difficult

36
Q

what do we specifically need to worry about related to bladders and uterus when giving opioids

A
  • Dogs may have difficulty urinating post-op
  • Problems with blocked cats
  • Opioids also slow uterine contractions, inhibit birth reflexes, depress neonatal resp.
37
Q

most common way fentanyl is administered

A

transfermal patch

38
Q

what is fentanyl used for

A
  • For profound pain relief in small animals
  • Also commonly used as an analgesic and sedative prior to induction
39
Q

do you need a reversal agent for etorphine? what is its potency compared to morphine

A

yes, its required for recovery

4000x more potent than morphine

40
Q

what is butorphenol used for

A

Used for mild/moderate pain; ineffective for severe pain

41
Q

what type of agonist is butorphenol

A

kappa agonist and mu antagonist

42
Q

main advantage of buprenorphine

A

-Main advantage is for home (oral transmucosal) administration for animals with chronic pain (long
duration)

43
Q

what is apomorphine used for

A

used to cause dogs to vomit

44
Q

can naloxone sotp vomit reflex

A

no

45
Q

what is an alternative to apomorphine

A

ropinirole

46
Q

what is a common anti-diarrheal in vet med

A

loperamide (imodium)

47
Q

what is the main opioid antagonist and how does it work

A

naloxone

bind and block mu opioid receptors through competitive inhibition