Alfentanil

Question 1

What is the brand/trade name for alfentanil?

Answer 1

• Alfenta

Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1

Question 2

What is the pharmacologic category/class of alfentanil?

Answer 2

• Opioid Analgesic — Synthetic
• Phenylpiperidine

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 4. Classification, Relative Potency & Opioid Abuse

*Nagelhout (7th ed.), p. 139 - Box 11.1

Question 3

What is the mechanism of action of alfentanil?

Answer 3

Opioid rececptor agonism, especially mu

• Presynaptic: decreases cAMP-dependent influx of calcium ions → inhibition of neurotransmitter release
• Post synaptic: increased outward K⁺ conductance → hyperpolarization of nerve cell

resultant increase in pain threshold, altered pain perception, and inhibition of ascending pain pathways

Note that these are similar to those of other opioids

_{Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 2. Opioid Receptors
Nagelhout (7th ed.), pp. 141 - Fig. 11.2, 142, 1295-1296, 1298
Stoelting’s Pharmacology (5th ed.), pp. 218-219}

Question 4

When used as an adjunct during induction and intubation what is the dosing range for alfentanil?

Answer 4

• 5-150 mcg/kg IV
  This helps to blunt the SNS response to laryngoscopy

Dose varies based on the anticipated length of the procedure

_{Nagelhout (7th ed.), p. 145 - Table 11.5
Stoelting’s Pharmacology (5th ed.), p. 237
UpToDate - Alfentanil: Drug Information}

Question 5

What is the onset of action for alfentanil?

Answer 5

• Rapid/Immediate

It is the fastest of all the opioids

_{Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 7. Alfentanil
Nagelhout (7th ed.), p. 146 - Table 11.6
Stoelting’s Pharmacology (5th ed.), p. 236}

Question 6

What is the duration of action for alfentanil?

Answer 6

• ~15-30 minutes, but varies depending on dose

Shorter than fentanyl

Half-life: ~1.5 hrs

_{Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Nagelhout (7th ed.), pp. 146 - Table 11.6, 147
Stoelting’s Pharmacology (5th ed.), pp. 236-237}

Question 7

What organ(s) are responsible for alfentanil’s clearance (metabolism/elimination)?

Answer 7

• Metabolism: Liver (P450)
• Elimination: Kidneys

No active metabolites, but susceptible to prolonged effects due to interactions/alterations in CYP3A4 function

_{Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 7. Alfentanil
Nagelhout (7th ed.), p. 147
Stoelting’s Pharmacology (5th ed.), p. 236}

Question 8

Cardiovascular effects of alfentanil include:

Answer 8

• Bradycardia
• Stable SVR/MAP
  _{no histamine release}

More likely to improve BP after increases related to painful stimulation

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3

Stoelting’s Pharmacology (5th ed.), p. 237

Question 9

What are the respiratory effects of alfentanil?

Answer 9

• Dose dependent depression of ventilation — RR affected before Vt
  _{(shifting of the CO2 response curve)}
• Inhibits hypoxic ventilatory drive
• Apnea at large doses

Note that these are similar to those of other opioids

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3

Nagelhout (7th ed.), p. 142

Stoelting’s Pharmacology (5th ed.), p. 222

Question 10

What are the effects of alfentanil on the CNS?

Answer 10

• Sedation
• Miosis/pinpoint pupils
• Mild hypothermia
  _{resets hypothalamic temperature setpoint}
• N/V (less than fentanyl/sufentanil)
  _{Partial dopamine agonists at CTZ}

Note that these are similar to those of other opioids

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3

Nagelhout (7th ed.), p. 142

Stoelting’s Pharmacology (5th ed.), pp. 223, 237

Question 11

What is the concentration (mcg/mL) of alfentanil vials?

Answer 11

• 500 mcg/mL

Duh, just remember it’s 10x less potent than fentanyl

Vials are often 2 mL, or 5 mL

UpToDate - Alfentanil: Drug Information

Question 12

Rapid IV administration of large doses of alfentanil can lead to generalized ______________; the greatest impact is on the ability to ______________

Answer 12

• Skeletal muscle rigidity
• Ventilate

_{some decrease in chest wall compliance, but this is mostly related to constriction of laryngeal musculature}

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 10. Skeletal Muscle Rigidity

Nagelhout (7th ed.), pp. 143-144

Stoelting’s Pharmacology (5th ed.), p. 223

Question 13

What are the GI/GU effects of alfentanil?

Answer 13

• Slowed peristalsis → CONSTIPATION
• N/V
  _{(less than fentanyl/sufentanil)}
• Contraction of sphincter of Oddi → biliary colic
  _{evidence is kind meh on this}
• Delayed gastric emptying
• Urinary retention (IDGAF)
  _{detrusor relaxation, urinary sphincter constriction}

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3

Nagelhout (7th ed.), pp. 143-144

Stoelting’s Pharmacology (5th ed.), pp. 223-224, 237

Question 14

The experience of pain can be divided into four steps: transduction, transmission, modulation, and perception. Which of these does alfentanil have an effect on?

Answer 14

Along with other opioids, alfentanil effects

• transduction
  _{peripheral nerves}
• modulation
  _{spinal cord}
• perception
  _{brain/brainstem}

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 1 & 2

Question 15

As an analgesic, alfentanil is __________ times more potent than morphine and _________ times LESS potent than fentanyl

Answer 15

• ~10
• ~10

This number varies slightly between texts

Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1

Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 4. Classification, Relative Potency & Opioid Abuse

Stoelting’s Pharmacology (5th ed.), p. 236

Question 16

Loading/induction doses of alfentanil should be administered as a “slow injection” or infusion over what time frame?

Answer 16

• 3 minutes

UpToDate - Alfentanil: Drug Information

Question 17

What is the rationale for avoiding alfentanil in epidural analgesia?

Answer 17

• Although it is effective, it has a very short duration of action

Nagelhout (7th ed.), p. 147