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Advanced Pharm > Opioids > Flashcards

Opioids Flashcards

1
Q

What are the three major sites of action of opioids?

A
  • Brain (supraspinal): pre and post synaptically to activate descending inhibitory pathways
  • Spinal cord: Directly on the dorsal horn of the spinal cord
  • In the periphery: Peripheral terminals of nociceptive neurons
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2
Q

What are opioids used for in anesthesia?

A
  • Attenuate the SNS response to noxious stimuli
  • Adjunct to IA during anesthesia
  • Sole anesthetic
    • fentanyl/Sufentanyl/Morphine: cardiac anesthesia or critically ill patients
  • Peri-op and post-op pain control
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3
Q

What characteristics unique to opioids set them apart from other analgesics?

A
  • effective for moderate to severe pain
  • no max dose or ceiling effect
  • tolerance can develop with chronic use
  • physical dependence, but not necessarily psychological dependence
  • cross tolerance between drugs
  • produce analgesia without loss of
    • touch
    • proprioception
    • consciousness (in smaller doses)
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4
Q

What are the different opioid classifiacations?

A
  • Naturally occuring- morphine and codeine
  • Semisynthetic- analogs of morphine
    • heroin, hydromorphone
  • Synthetic-Exogenous
    • Agonist
    • partial agonist
    • mixed agonist/antagonist
    • antagonist
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5
Q

What are agonists?

Antagonists?

A
  • Agonist- drugs that occupy receptors and activate them
  • antagonist- drugs that occupy receptros but do not activate them; block receptor from agonist
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6
Q

What is the MOA of opioids?

A
  • Activate stereospecific GCPR:
  • Post synaptic- directly decreases neurotransmission
    • increased K conductance (hyperpolarization)
    • Ca channel inactivation (decreased neurotransmitter release)
    • Modulation of phosphoinositide signaling cascade and phospholipase C
    • inhibition of adenylate cyclase (decreased cAMP) *delayed
  • Pre-synaptic- inhibits the release of excitatory neurotransmitters
    • decreased ACh, dopamine, NE, substance P release
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7
Q

What are the opioid receptors?

What is the theory?

A
  • MU, kappa, delta
  • theory: synthetic opioids mimic action of endogenous opioids by binding to opioid receptors
    • activating pain modulating systems
  • The different drugs have varying affinity for the receptors?
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8
Q

Mu receptor

Subtypes?

Where are they?

A
  • Subtypes Mu-1, mu-2, mu-3
    • Mu-3 may be involved in immune process
  • All endogenous and exogenous agonists act on mu receptors
  • Mu receptors are found in the brain, periphery, and spinal cord
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9
Q

What are the differences between the receptors?

Supraspainal and/or spinal?

effects?

Agonists

(chart)

A

*Endorphins= all endogenous and exogenous agonists work on these receptors

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10
Q

What receptor do opioid agonist-antagonists often prinicpally interact with?

A

Kappa

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11
Q

Which CYP commonly has mutations that can alter the metabolist of opioids?

Which opioids are affected?

What opioid is least likely to be affected?

A
  • CYP2D6
  • Causes unpredictable pharmacokinetics and 1/2 lves of:
    • codeine
    • oxycodone
    • hydrocodone
    • methadone
  • Fentanyl is least likely to be affected
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12
Q

Rate of opioid metabolism may influence ______ _______.

Ultra-rapid metabolizers are at increased risk for ______.

A

Side effects

PONV

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13
Q

What are perioperative CV effects of opioids?

A
  • minimal CV impairment when used alone, additive when used with other anesthetics
  • dose dependent bradycardia
    • Central vagal stimulation
    • direct SA, AV nodal depression
  • ​Vasodilation/decreased SVR
    • impairment of SNS responses and baseline tone
    • pronounced w/hypovolemia
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14
Q

What CV effects are unique to morphine and meperidine?

A
  • dose/infusion rate dependent histamine release.
    • bronchospasm
    • dramatic drops in SVR and BP
    • Variable response among individual patients
  • Meperidine can cause tachycardia with more prominent direct myocardial depression
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15
Q

What are the CNS effects of opioids?

A
  • Analgesia
  • euphoria
  • drowsiness/sleep
  • miosis
  • nausea- chemoreceptor trigger zone (CRTZ)
  • If hypoventilation prevented:
    • modest decrease in ICP
    • decreased CBF
  • NO amnesia
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16
Q

What are the Renal/GI/Liver effects of opioids?

A
  • increased tone and peristaltic activity of ureter and detrusor muscle tone = increased urgency, with decreased ability to void
  • decreased catecholamine release and cortisol
  • Sphinctor of oddi spasm and gallbladder contraction with increase in biliary pressure
  • spasm of GI smooth muscle
    • constipation- decreased GI motility
    • prolonged gastric emptying
17
Q

What are the GI effects of opioids?

A
  • Decreased gastric emptying
  • Direct stimulation of CRTZ on the floor of the 4th ventricle
    • partial dopamine agonist?
  • Morphine depresses the vomiting center in the medulla
18
Q

What is the cause of pruritis?

Where does it primarily occur?

A
  • Cause unknown
    • most probably explanation is histamine release (MSO4)
  • primarily on face and particularly nose
    • fentanyl nose itch
19
Q

What are the Skeletal muscle effects of opioids?

A
  • Skeletal muscle rigidity in chest, abdomen, jaw, and extremeties
    • esp w/large, rapid boluses
      • fentanyl, sufentanil, and hydromorphone
    • can make ventilation difficult or impossilbe
    • high airway pressures from increased intrathoracic pressures decreases venous return
  • Glottic rigidity and glottic closure have been reported
20
Q

What are the ventilatory effects of opioids?

A
  • Dose dependent respiratory depression
    • small doses: increased TV, decreased RR; overall decrease MV
    • larger doses: decreased RR and TV
  • Decreased chest wall compliance
  • Donstriction of pharyngeal and laryngeal muscles
  • cough suppresion
  • decreased response to hypercarbia and hypoxia
  • Morphine and meperidine= histamine release–>bronchoconstriction
21
Q

What factors can affect the magnitude and duration of opioid induced respiratory depression?

A
  • amount of pain/surgical stimulation
  • intermittent bolus vs cont. infusion
  • speed of injection
  • concurrent admin with other anesthetics
  • decreased clearance
  • age
22
Q

Morphine:

use

administration

metabolism

A
  • IM or IV for severe acute pain, PO for chronic or cancer pain
  • slow release formulations available- onset delayed 3-5 hours, not used perioperatively
  • Metabolism
    • considerable first pass effect
    • 1/2 life 3-4 hours, converted to active metabolite (morphine-6-glucuronide)
23
Q

Codeine

use

administration

E1/2t

matabolism

Exception

A
  • Use: mild pain relief, cough
  • PO
  • E1/2t = 3 hours
  • Metabolism: prodrug, 10% is metabolized by CYP2D6 to active form and remainder is demethylated to inactive metabolite
    • active form has equal analgeia to morphine
  • 10% caucasians and 30% asians lack 2D6 and experience no analgesic effect
24
Q

Hydrocodone:

use

route

problems

A
  • AKA Vicodan
  • PO
  • Analgesia (chronic pain), antitussive
  • Always combined with eithr ASA, ibuprofen, antihistamine, acetaminophen
  • High abuse potential
25
Q

Oxycodone

AKA

use

problems

A
  • AKA oxycontin, percocet, percodan
  • PO- available in sustained release preparation (oxycontin)
  • Use: moderate to severe pain, useful for chronic and post-op pain
    • in combination with ASA or acetaminophen
  • No active metabolites- safer in pts with renal dysfunction
  • High abuse potential
  • According to Dr E: Terrible, dont give it to anyone
26
Q

Methadone

route

class

plasma half life/metabolites

use

A
  • PO, IV, SC
  • synthetic
  • No active metabolites; long plasma half life 8-100 hours
  • Use: opioid addiction treatment (dosed q day)
    • chronic pain: BID or TID
    • at risk for respiratory depression d/t prolonged and unpredictable E1/2t
27
Q

How long does it take to develop tolerance to opioids?

What is the progression?

A
  • 2-3 weeks of opioid use
  • Pt first shows reduction in adverse effects
    • tolerance to sedative and emetic effects more rapid than constipation
  • shorter duration of analgesia
  • then effectivenesss of each dose decreases
28
Q

Which class of opioids can cause cross tolerance?

A
  • Cross tolerance exists among all full agonists but is not complete
  • When switching to another opioid, start with half or less of the normal analgesic dose
29
Q

Random stuff about opioid dependence (4)

A
  • Physical dependence causes abstinence symptoms upon sudden D/C
  • Clinically significant dependence develops only after several weeks of chronic treatment
  • addiction involves psychological dependence and biologic and social factors
  • Cancer pain and acute pain patients rarely experience euphoria and even more rarely develop psychological dependence or addiction
30
Q

How are opioids dosed?

A
  • Doses vary widely from one pt to another
  • no minimum or max, unless combined with acetaminophen or ASA
  • dose is based on how much is required to alleviate symptoms with tolerable side effects
  • sustained release should be used for chronic pain
31
Q

If pain is well controlled and switching opioids, calculate the equivalent dose and reduce by ____ for the dose of the new drug.

A

25%

32
Q

What are the neuraxial effects of opioids?

A
  • Analgesia is a result of diffusion of the drug across the dura to mu receptors in the substantia gelatinosa
    • if drug is more lipophillic, will pass into the vasculature and have a systemic effect
  • Opioids given epidural or spinal have a different onset, duration, and side effects as same drug given IV
  • Amt of cephalad movement of opioid in the CSF depends on lipid solubility
33
Q

How does lipid solubility of opioids affect neuraxial antsthesia?

A
  • Opioids that are highly lipid soluble will have limited migration b/c of uptake into the spinal cord and vasculature
    • ex. Fentanyl
  • Less lipid soluble opioids will remain in CSF and will migrate
    • ex. Morphine
34
Q

Dose for epidural is ____ times ______ than spinal dose

A

5-10x

higher

Advanced Pharm (27 decks)

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