Opioids

Question 1

Opiate’s mechanism of action?

Answer 1

Stimulation of opioid receptors in the CNS.

Question 2

What are the effects of opioids? (9)

Answer 2

Analgesia
Sedation
Euphoria
Pupil constriction 
Urinary retention
RR depression 
N/V
Pruritis
Bradycardia

Question 3

What opioids mostly used for?

Answer 3

For pain relief.

Mild sedation, no amnestic properties.

Question 4

How come fentanyl is preferred over morphine? (3)

Answer 4

1. Rapid onset (600x more lipid soluble than morphine)
2. Less risk of hypotension (does not promote histamine release)
3. Absence of active metabolites.

Question 5

What’s the onset time of fentanyl?

Answer 5

1-2min

Question 6

What is the fentanyl dose adjustment for renal failure?

Answer 6

There are none.

Question 7

Where are opioids primarily metabolized?

Answer 7

Metabolized primarily in the liver, metabolites are excreted in the urine.

Question 8

Morphine can accumulate in renal failure. Name 2 adverse effects of these metabolites.

Answer 8

1. morphine 3glucuronide causes CNS excitation w/myoclonus and seizures.
2. Morphine 6 Glucuronide has more portent analgesic effects.

Question 9

How should morphine be renally dose?

Answer 9

Dose should be reduced by 50% in pt w/renal failure.

Question 10

Morphine promotes the release of histamine. What are considerations?

Answer 10

1. Can cuase systematic vasodilation –>hypotension. It’s often seen in hyperadrenergic state and increased periheral vascular tone.
2. THOU does not promote bronchoconstriction at certain doses.

Question 11

Hydromorphone is a morphine derivative, what are some advantages? (3)

Answer 11

1. Does not have to be renally dose like morphine.
2. Recently study shows it has more effective analgesia.
3. No histamine release

Question 12

What are the onset times of morphine?

Answer 12

5-10 min

Question 13

What are the onset times of hydrocodone?

Answer 13

5-15min

Question 14

How is remifentanil typically given?

Answer 14

It’s super short actiing,so typically via continuous IV infusion.

Question 15

Dosing Regimen of remifentanil?

Answer 15

1.5 microgram/kg as a loading dose. Followed by continuous infusion of 0.5-15micrograms/kg/hr

Question 16

How is remifentanil broken down?

Answer 16

By non specific esterases in plasma. No need for dose adjustment in renal/hepatic failure.

Question 17

How short acting is remifentanil?

Answer 17

10 minutes.

Question 18

What clinical situations would you use remifentanil?

Answer 18

1. Due to short acting nature, it’s useful in conditions of frequent evalutations of cerebral function i.e TBI.
2. Abrupt cessation of opioid activity can cause acute opioid withdrawal. Can prevent by using remifentanil w/longer acting opioid.

Question 19

Where is meperidine metabolized, and what is its subsequent metabolite?

Answer 19

In the liver, to normeperidine. a NEUROTOXIC metabolite.

Question 20

What is normeperidine’s half life, and negative side effects?

Answer 20

1. 15-40 hours.

2. Accumulation can cause CNS excitation, agitation, myoclonus, delirium and generalized seizures.

Question 21

How come meperidine (demerol, pethidine) no longer favored for pain control?

Answer 21

It’s potential for neurotoxicity.

Question 22

Opioids can decrease bp/HR. How come?

Answer 22

This is due to decreased sympathetic activity and increased parasympathetic activity. Typically tolerable, esp whenpt in supine position.

Question 23

In what clinical settings could opioid induced hypotension be more pronounced?

Answer 23

In hypoveolmic or HR patients. In these situations, there is an increased baseline sympathetic tone that is affected by the opioid.
Another situation is opioids given with benzodiazepines.

Question 24

How serious could opioid induced hypotension be?

Answer 24

Rarely a threat to tissue perfusion, BP typically responds well to IV fluids or small bolus doses of vasopressors.