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Prodigy Quick Review > Opioid Agonists > Flashcards

Opioid Agonists Flashcards

1
Q

All endogenous opioids are derived from three

prohormones. Name them.

A

Proenkephalin, prodynorphin, and pro-opiomelanocortin.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 145.

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2
Q

What is the difference between an agonist and an

antagonist?

A

An agonist is a drug that binds with a receptor and produces the
effect that the receptor is capable of producing. For example,
an opioid such as fentanyl that binds with a receptor capable of
producing analgesia will produce that effect. An antagonist is a
drug that will bind to the receptor but not exert the action the
receptor is capable of producing. The effect of an antagonist is
to prevent other agonists from binding with the receptor and
producing their effect. Naloxone is an example of an opioid
antagonist.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 170.

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3
Q

What is a partial agonist?

A

A partial agonist is not able to produce the maximum effect of
agonism of a particular receptor.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 170.

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4
Q

What is a agonist-antagonist?

A

An agonist-antagonist has affinity for a receptor but its intrinsic
activity is just a fraction of the pure antagonist.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 58.

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5
Q

In the context of opioid receptors, what does the

term ‘affinity’ mean?

A

Affinity is the ability of a drug to bind with a receptor to form a
stable complex.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 170.

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6
Q

In the context of opioid receptors, what does the

term ‘efficacy’ mean?

A

Efficacy refers to the dose-response curve produced by the
binding of the opioid to an opioid receptor. It is a measure of
the effect the drug produces ranging from no effect at all to the
maximum effect activation of the receptor can produce.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 17.

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7
Q

What is the difference between potency and efficacy?

A

Efficacy refers to the maximum effect a drug can produce when
binding to a receptor. Potency refers to the relative dose of a
drug that is required to produce the effect and is closely
associated with the affinity of the drug for the receptor.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 170.

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8
Q

What are the three classifications used to describe
the location at which opioids exert their analgesic
effect?

A

Peripheral-refers to analgesic action in the peripheral tissues.
Spinal-refers to analagesic action exerted at the level of the
spinal cord. Supraspinal-refers to analgesic action above the
spine (higher neural centers in the brain such as the midbrain
and medulla).
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 145.

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9
Q

What are the two major methods by which opioids

produce analgesia?

A

1) the direct blockade of ascending nociceptive signals from the
dorsal horn of the spinal cord and 2) stimulate pain modulation
pathways that descend from the midbrain to the dorsal horn of
the spinal cord via the ventromedial medulla.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

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10
Q

Is the analgesic effect of Mu receptors produced

supraspinally, spinally, or peripherally?

A

Supraspinal
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 146.

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11
Q

Is the analgesic effect of Kappa receptors produced

supraspinally, spinally, or peripherally?

A

Supraspinal and spinal
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147.

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12
Q

Is the analgesic effect of Delta receptors produced

supraspinally, spinally, or peripherally?

A

Supraspinal and spinal
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147.

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13
Q

What opioid receptor(s) are responsible for

producing respiratory depression?

A

Mu, Delta, and Kappa
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147.

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14
Q

What opioid receptor(s) are responsible for

producing nausea and vomiting?

A

Mu
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147.

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15
Q

What opioid receptor(s) are responsible for

producing pruritus?

A

Mu and Delta
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147.

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16
Q

Do morphine and other mu-receptor agonists
produce a shift to the right or a shift to the left in the
CO2 responsiveness of the medullary respiratory
centers?

A

They decrease the responsiveness of the medullary respiratory
center to CO2, which represents a shift to the right.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

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17
Q

How do opioids depress the cough reflex?

A

They exert a direct effect on the medullary cough center.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

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18
Q

How do opioids affect the biliary tract?

A

They increase the sphincter tone of the common bile duct and
the sphincter of Oddi and can result in increased biliary
pressure or biliary spasm.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 519.

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19
Q

How can you counteract the biliary effects of opioids?

A

Naloxone and glucagon have been shown to reverse opioidinduced
contraction of the common bile duct and sphincter of
Oddi.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 195.

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20
Q

How do opioids cause nausea?

A

By direct stimulation of the chemoreceptor trigger zone.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 518.

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21
Q

How does opioid use affect the medullary
chemoreceptor trigger zone and why is this
important?

A

Opioids stimulate the chemoreceptor trigger zone, producing
the sensation of nausea. This effect is important because of the
priority placed on early discharge. Protracted nausea can
prolong recovery room stays and increase costs.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 195.

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22
Q

How do opioids affect urinary function?

A

The effect of opioids on urine production depends on which
opioid receptor is most stimulated. Kappa receptor agonists
cause diuresis, but Mu receptor agonists produce an antidiuretic
effect. Urinary retention is also common with neuraxial opioid
administration.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 147-149.

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23
Q

What are the gastrointestinal effects of opioid

administration?

A

Opioids inhibit gastric secretion, decrease gastric motility, and
suppress diarrhea. They can also delay gastric emptying and
cause bowel distention, constipation, and paralytic ileus.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 519

24
Q

How do opioids affect respiratory rate? Tidal

volume? Minute ventilation?

A

Opioids reduce respiratory rate, tidal volume, and minute
ventilation. Respiratory rate is reduced first.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

25
Q

By what mechanism do opioids produce respiratory

depression?

A

Opioids exert a dose-dependent depressant effect on
respirations by their effects on mu and delta receptors in the
brainstem. The respiratory centers become less responsive to
increases in carbon dioxide and decreases in oxygen
concentration. The CO2 response curve shifts to the right. The
respiratory rate is affected first.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

26
Q

How do opioids produce miosis?

A

Miosis is produced by opioids by stimulating the autonomic
portion of the nucleus of the oculomotor nerve. It occurs within
the pupillary reflex arc. Opioids stimulate the Edinger-Westphal
nucleus which transmits a parasympathetic impulse to the
ciliary ganglion to cause the oculomotor nerve to constrict the
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 149.

27
Q

What is the most prudent action to take when faced
with severe, opioid-induced muscle rigidity at
induction?

A

Large doses of narcotics, particularly fentanyl, sufentanil, and
alfentanil, can result in chest wall rigidity that can make
ventilation difficult or impossible. Administration of a fast-acting
muscle relaxant such as succinylcholine or administering
naloxone can relieve the rigidity and make ventilation possible.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 150.

28
Q

How do nitrous oxide, naloxone, and GABA receptor
agonists influence the muscle rigidity seen with the
administration of high doses of opioids.

A

Nitrous oxide significantly increases the incidence and degree
of muscle rigidity seen with high-dose opioid administration.
Naloxone and GABA receptor agonists such as propofol,
thiopental, and benzodiazepines inhibit this response.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 150.

29
Q

How do high-dose opioids produce muscle rigidity?

A

Large doses of opioids have been shown to produce muscle
rigidity via central mu receptor interaction with dopamine and
GABA pathways.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 150.

30
Q

From what cells does morphine stimulate histamine

release?

A

Morphine stimulates the release of histamine from tissue mast
cells.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 153.

31
Q

How does morphine-6-glucuronide reach the CNS?

A

M6G is not lipid soluble. Despite its CNS potency, only small
amounts cross the blood-brain barrier. After chronic
administration, however, it can accumulate and begin to cross
the blood-brain barrier by mass action.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 153.

32
Q

How do the potency of the metabolites of morphine

compare to that of the parent drug?

A

Morphine-6-glucuronide appears to exert a CNS effect that is
more potent than morphine. Morphine-3-glucuronide is inactive.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 153.

33
Q

Why does morphine often cause prolonged sedation

in patients with renal impairment?

A

Morphine’s metabolite, morphine-6-glucuronide is a powerful
CNS depressant. It is eliminated by the kidneys and will
accumulate in high enough levels in patients with kidney
disease that it begins to cross the blood-brain barrier despite its
low lipid solubility.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 153.

34
Q

What non-opioid drug is meperidine structurally most
similar to? What similar actions does meperidine
exhibit that are similar to this drug?

A

Like its structurally similar counterpart, atropine, meperidine can
produce dry mouth and blurred vision.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 194.

35
Q

What is the active metabolite of meperidine and what

are its effects?

A

Normeperidine is the active metabolite of meperidine. It has an
elimination half-life that is much longer than that of meperidine
and most significantly, reduces the seizure threshold. As
normeperidine accumulates, it can cause symptoms of CNS
excitation such as tremors, muscle twitching, and seizures.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

36
Q

Is meperidine’s ability to reduce shivering mediated

by mu receptors?

A

No. It is thought to be mediated by kappa receptors or by a nonopioid
mechanism altogether.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

37
Q

What are the onset and peak effect times for
intravenous fentanyl? What is the significance of
this relationship?

A

The onset of fentanyl is typically listed at about two minutes, but
laboratory studies have demonstrated onset times as short as
ten seconds. The peak effect occurs at about 20 minutes. The
significance is that without closely monitoring the time between
doses, the desire to relieve an awake patient’s pain rapidly can
result in overadministration of fentanyl with resultant respiratory
depression.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 153.

38
Q

What is the duration of action of fentanyl?

A

Between 20 and 40 minutes.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

39
Q

What is the primary determinant of the clearance of

fentanyl?

A

Hepatic blood flow.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

40
Q

Does fentanyl have active metabolites?

A

No, fentanyl is dealkylated and hydroxylated to inactive
metabolites. These metabolites are excreted in the urine and
bile.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

41
Q

Why is the oral route of administration for fentanyl

not as effective as other routes?

A

Fentanyl undergoes extensive first-pass metabolism, so the oral
route is typically insufficient for administration.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 716.

42
Q

What is the disadvantage of using fentanyl as the
sole agent for anesthesia and what doses are
typically required?

A

High doses of fentanyl blunt the stress response to surgery and
provide a high degree of hemodynamic stability, but at the risk
of increased risk of awareness, incomplete suppression of
autonomic responses, and prolonged respiratory depression.
Chest rigidity is also a risk in high doses are administered at
induction. Remifentanil is now the recommended agent to
provide profound analgesia without the need for postoperative
ventilation.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 4-5.

43
Q

How does fentanyl affect MAC? Specifically, what

dose of fentanyl affects MAC by what amount?

A

Fentanyl decreases MAC in a dose-dependent fashion. Studies
demonstrate that 3 mcg/kg of intravenous fentanyl decrease the
MAC of isoflurane and desflurane by 50%.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 512-513.

44
Q

How much drug do fentanyl patches deliver?

A

Fentanyl patches typically deliver 75-100 mcg/hour.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

45
Q

How long after placement of a fentanyl patch does

the drug’s peak effect occur?

A

A fentanyl patch won’t produce a peak effect until 18 hours after
placement of the patch. A consistent dose of fentanyl won’t be
delivered to the bloodstream until the subcutaneous tissue is
saturated with the drug.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

46
Q

How does the potency of sufentanil compare to that

of morphine and fentanyl?

A

Sufentanil has a potency about 5-10 times that of fentanyl.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 109.

47
Q

What is the elimination half-life of remifentanil?

A

8-20 minutes
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

48
Q

How is remifentanil metabolized?

A

It is rapidly metabolized by blood and tissue esterases.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

49
Q

Does remifentanil exhibit the potential for prolonged

effects due to the accumulation of the drug?

A

No, it is metabolized so rapidly by esterases that it doesn’t
accumulate and exhibits little potential for exaggerated effects
due to repeat dosing or infusion.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 717.

50
Q

Is the metabolism of remifentanil affected by

succinylcholine administration?

A

No, remifentanil is hydrolyzed by nonspecific esterases, not
plasma cholinesterases like succinylcholine.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

51
Q

Can remifentanil be used epidurally or intrathecally?

Why or why not?

A

No. Remifentanil contains glycine as a buffer. Because glycine
can cause neurotoxicity, it cannot be administered epidurally or
intrathecally.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154-155.

52
Q

Why is remifentanil not recommended for use in
monitored anesthesia care or the postoperative
setting?

A

It has a high potential for respiratory depression and muscle
rigidity that makes it unsuitable for use in these settings.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

53
Q

How does the onset, duration, and lipid solubility of

alfentanil compare to fentanyl?

A

Despite the fact that alfentanil has a lower lipid solubility than
fentanyl, its onset is faster and its duration is shorter.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

54
Q

Why is alfentanil avoided in patients with epilepsy?

A

Small doses of alfentanil (< 50 mcg/kg) have been associated
with activation of seizure foci in patients with epilepsy.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 583.

55
Q

What antibiotic prolongs the metabolism of alfentanil?

A

Erythromycin prolongs the metabolism of alfentanil and results
in prolonged respiratory depression and sedation.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 154.

56
Q

Between fentanyl, sufentanil, alfentanil, and
morphine, which drug would be most suitable for use
in neuroanesthesia and why?

A

Fentanyl is the most appropriate choice for neuroanesthesia.
Although all opioids could potentially reduce cerebral perfusion
pressure due to hypotension, this effect would be more likely to
occur with sufentanil or alfentanil than fentanyl. Also, sufentanil
and alfentanil have been reported to result in increases in
intracranial pressure in patients with intracranial tumors. In
patients with epilepsy, small doses of alfentanil can activate
seizure foci. Morphine is not generally used in neuroanesthesia
because it has a low lipid solubility and can produce
hypotension through histamine release.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 583.

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