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Anesthesia/AEDs/Psych drugs > Opioids > Flashcards

Opioids Flashcards

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1
Q

Name the opioid agonists (not including agonist/antagonists)

A 
Morphine
Codeine
Meperidine
Fentanyl
Sufentanil
Alfentanil
Remifentanil
Methadone
Hydromorphone
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2
Q

What is the mechanism of action of opioid agonists?

A

Opioid agonist binds GPCR –> inhibits adenylyl cyclase –> 2 signaling effects:

1) Decrease conductance of voltage-gated Ca channels –> decreased transmitter release
2) Increase K outflow post-synaptically –> hyperpolarization

Both of these effects result in prevention of excitation and propagation of action potential –> analgesia (mostly mu receptor) and other side effects

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3
Q

What are side effects of Mu receptor activation?

A

Constipation (due to decreased ACh release –> slower gastroparesis and peristalsis –> more water absorption)
Euphoria
Physical dependence
Respiratory depression (depressant effect on brainstem ventilation centers - loss of CO2 responsiveness, but retain hypoxic drive)
Sedation

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4
Q

What are side effects of Delta receptor activation?

A

None, just involved in analgesia

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5
Q

What are side effects of Kappa receptor activation?

A

Constipation (due to decreased ACh release –> slower gastroparesis and perstalsis –> more water absorption)
Miosis (can be antagonized with atropine)
Psychotomimesis
Sedation?

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6
Q

Which opioid agonists are anti-tussive?

A

D-methorphan

Codeine

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7
Q

When do opioid agonists cause muscle rigidity?

A

Large doses, rapid injection

Interacts with opioid receptors in striatum and substantia nigra and inhibit DA release

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8
Q

What effect do opioid agonists have on the cardiovascular system?

A

No direct effect on myocardium, but can cause hypotension due to the following:

  • Bradycardia due to decreased central sympathetic tone
  • Increased activity over vagal nerve
  • Direct depressant effect on SA node
  • Histamine release (morphine and meperidine)
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9
Q

Do opioid agonists cause urinary retention or incontinence?

A

Urinary retention

Causes increased tone and peristalsis of ureter, which would normally cause incontinence
But also increases tone of sphincter, which outweighs ureter tone and peristalsis

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10
Q

Why does morphine have delayed penetrance of BBB?

A

Poor lipid solubility
Highly ionized
Binds protein
Rapidly conjugated in liver

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11
Q

What are the metabolites of morphine and which are active?

A

M3G - inactive

M6G - active - can cause increased ventilatory depressant effects in renal failure patients

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12
Q

What is unique about the structure of meperidine and why is it significant?

A

Structurally similar to atropine - can cause atropine-like side effects at high doses (tachycardia, mydriasis)

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13
Q

What is the metabolite of meperidine and what are its effects?

A

Normeperidine

Causes myoclonus and seizures in renal failure patients

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14
Q

What are the two drugs that cause histamine release?

A

Morphine

Meperidine

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15
Q

What is the main clinical use of meperidine?

A

Post-operative shivering

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16
Q

Is meperidine more or less potent than morphine?

A

Less - 1/10 as potent

17
Q

Is fentanyl more or less potent than morphine?

A

More - 75-125x as potent

18
Q

Compare the onset and duration of fentanyl (and its derivatives) to that of morphine (and its derivatives)

A

Fentanyl - more rapid onset, but shorter duration than morphine
(rapid onset due to better lipid solubility)
(shorter duration due to rapid redistribution to inactive sites)

19
Q

What are the metabolites of fentanyl and what are their effects?

A

No metabolites! Trick question!

20
Q

What cardiovascular effects does meperidine have?

A

Large doses decrease myocardial contractility

21
Q

Is sufentanil more or less potent than fentanyl?

A

More - 5-10x as potent

22
Q

Is alfentanil more or less potent than fentanyl?

A

Less - 1/5-1/10 less potent

23
Q

How is alfentanil cleared?

A

Hepatic clearance - CYP3A

24
Q

Is remifentanil more or less potent than fentanyl?

A

About the same

25
Q

What is unique about remifentanil?

A

Unique ester linkage
Allows it to be metabolized by tissue plasma esterases

So metabolism will be unaffected by hepatic or renal failure - ideal in these patients

26
Q

What receptor (in addition to Mu) does Methadone act at?

A

NMDA antagonist

27
Q

Why can methadone be difficult to dose?

A

Has prolonged action after repeated doses
Accumulates in tissues, causing prolonged and unpredictable half-life and negative side effects
(Analgesia half-life different from half-life of side effects)

28
Q

Is hydromorphone more or less potent than morphine?

A

More - 5x as potent

29
Q

In what patients will hydromorphone be a much better choice than morphine?

A

Patients with renal failure

Hydromorphone does not have the buildup of M6G active metabolite

30
Q

What drugs are opioid agonists/antagonists?

A

Buprenorphine
Butorphanol
Nalbuphine

31
Q

When is an agonist/antagonist a better choice than a pure agonist?

A

When patient cannot tolerate a pure agonist

i.e. cannot tolerate ventilatory depression, has a high potential for physical dependence

32
Q

What is the mechanism of opioid agonists/antagonist?

A

Act as agonist at one receptor (usually mu)

Act as antagonist at another receptor (delta or kappa)

33
Q

What drugs are opioid antagonists?

A

Naloxone

Naltrexone

34
Q

What is the mechanism of opioid antagonists?

A

Binds opioid receptors with high affinity and can displace the agonist –> reverses effect of agonist (ventilatory depression AND pain suppression)

35
Q

When are opioid antagonists used?

A

To treat opiate induced ventilatory depression or opioid overdose (rescue situations)

36
Q

What are potential problems to monitor for when using an opioid antagonist in a rescue situation?

A

CV stimulation due to increased sympathetic activity

Re-narcotize (antagonists have short duration and half-life, so excess opioid agonist may be hanging around once the antagonist has been metabolized, potentially re-causing opioid agonist effects)

Anesthesia/AEDs/Psych drugs (4 decks)

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