Opioids Flashcards

1
Q

List the main pharmacological effects of opioids.

A

Analgesia
Sedation
Excitation
Bradycardia
Respiratory depression
Nausea/vomiting/decreased GI motility
Antitussive?
Urinary/pupillary effects

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2
Q

Describe full agonists and give two examples.

A

Bind to and activate a receptor with the maximum response that an agonist can elicit at that receptor
Methadone and fentanyl

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3
Q

Describe partial agonists and give an example.

A

Bind to and activate a receptor but only have partial efficacy, even if they bind to all receptors
Buprenorphine

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4
Q

Give an example of a mixed agonist-antagonist.

A

Butorphanol

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5
Q

Give an example of an antagonist.

A

Naloxone

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6
Q

Which type of opioid is most associated with analgesia?

A

Mu agonists
Full mu agonists provide the most effective analgesia

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7
Q

By what routes can be opioids be administered?

A

IM
IV
SC
OTM/buccal
Transdermal
Epidural/spinal

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8
Q

Why are opioids not useful when administered orally?

A

Significant first pass metabolism resulting in poor oral bioavailability

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9
Q

What are the (dis)advantages of IV opioids?

A

A = rapid onset of action, reliable uptake, painless (regardless of volume)

DA = Need IV access

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10
Q

What are the (dis)advantages of IM opioids?

A

A = reliable uptake

DA = Painful (large volumes)

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11
Q

What are the (dis)advantages of SC opioids?

A

A = easy to perform

DA = unreliable uptake

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12
Q

What are the (dis)advantages of OTM opioids?

A

A = easy to perform

DA = Only certain opioids

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13
Q

What are the (dis)advantages of transdermal opioids?

A

A = good for chronic use

DA = no licensed products

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14
Q

What are the (dis)advantages of epidural/spinal opioids?

A

A = very effective analgesia (mostly intra-op)

DA = No licensed products, technically difficult

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15
Q

List some ultra-short-acting (mins) opioids.

A

Fentanyl
Alfentanil, Sufentanil, Remifentanil

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16
Q

List some short-acting (2hrs) opioids.

A

Butorphanol
Pethidine

17
Q

List some medium-acting (2-4hrs) opioids.

A

Methadone
Morphine

18
Q

List a longer-acting (6hrs) opioid.

A

Buprenorphine

19
Q

How can we increase duration of action of opioids?

A

Oral sustained release formulations
IM/SC - adding a vasoconstrictor
Transdermal delivery systems e.g. human fentanyl patches

20
Q

What are some common misconceptions surrounding opioids?

A

Opioids cause mania in cats
Opioids cannot be re-dosed within their expected ‘duration of action’
Respiratory depression can occur
Opioids cannot be combined with other classes of analgesic drug

21
Q

Describe respiratory depression as a side effect of opioid admin.

A

Rarely clinically significant in awake animals
Most likely to be seen when administered during anaesthesia

22
Q

Describe bradycardia as a side effect of opioid admin.

A

Vagally mediated, can be treated with anticholinergics e.g. atropine/glycopyrrolate
Low doses of anticholinergics might promote worsening of bradycardia - give more!
High doses promote tachycardia - wait!

23
Q

List the opioids in order of analgesic efficacy.

A

MOST - fentanyl
Methadone + morphine
Pethidine
Buprenorphine
LEAST - butorphanol

24
Q

Describe fentanyl.

A

Some resp. depression when given during anaesthesia (dose dependent)
Likely to induce a bradycardia
Most useful as CRI due to short-acting
Boluses can be useful to minimise nociception to acute noxious stimuli during surgery

25
Q

Describe methadone.

A

Reduced nausea/vomiting compared to morphine
No concern re histamine release given IV
Minimal CVS and resp. side effects
NMDA receptor antagonist effects

26
Q

Describe pethidine.

A

Short-acting limits post-op use
Large volume = painful IM
Histamine release if given IV
Replaced in practice by methadone

27
Q

Describe buprenorphine.

A

Multi-dose preparation has preservative (pain on injection/not palatable OTM)
Good evidence to support use in cats
May not be effective SC
? Delayed onset of action (analgesia + sedation)
Schedule 3 opioid but to be treated like a schedule 2

28
Q

Describe butorphanol.

A

Analgesia short-lived, need high doses
May confound subsequent full mu-agonist administration
Sedation good
Not subject to CD regulations

29
Q

Describe naloxone.

A

Specific antagonist so can be used to reverse effects of an opioid
Analgesia will also be reversed! - provide alternative

30
Q

How can we select appropriate premedication opioids?

A

Sedation only = butorphanol
Mild pain = buprenorphine
Moderate pain = pethidine/methadone, buprenorphine
Moderate to severe pain = methadone

31
Q

How can we select appropriate intra-op opioids?

A

Sedation = unnecessary
Mild pain = unnecessary
Moderate pain = methadone, fentanyl bolus/CRI
Moderate to severe pain = methadone, fentanyl bolus/CRI, (epidural morphine)