Labetalol

Question 1

What is the pharmacologic category/class of labetalol

Answer 1

• Nonselective beta-1 & 2 adrenergic antagonist
• Selective alpha-1 antagonist

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Question 2

What is the mechanism of action of labetalol?

Answer 2

SA nodal cells: inhibits cAMP mediated sodium & calcium conductance during phase 4 of the action potential → ↓ chronotropy

Cardiac myocytes: inhibits cAMP mediated calcium conductance → ↓ inotropy

Vascular smooth muscle: inhibits intracellular signalling and decreases calcium release from sarcoplasmic reticulum → vasodilation

not suitable for pts. with reactive airway disease d/t beta 2 blockade

_{Anesthesia Guidebook - Episode 18: Anesthesia Top Drawer Run Down - Part 2
UpToDate - Labetalol: Drug Information}

Question 3

What is the typical dose of labetalol in the perioperative period?

Answer 3

• 5-20 mg over 2 minutes, repeated q5-10 minutes PRN

maximum cumulative dose not to exceed 300 mg

IV bolus can be titrated up to a max single dose of 80 mg

_{Anesthesia Guidebook - Episode 18: Anesthesia Top Drawer Run Down - Part 2
UpToDate - Labetalol: Drug Information}

Question 4

What is the onset of action for labetalol?

Answer 4

• 1-5 minutes, peak effect within 15 minutes

_{Anesthesia Guidebook - Episode 18: Anesthesia Top Drawer Run Down - Part 2
UpToDate - Labetalol: Drug Information}

Question 5

What is the duration of action for labetalol?

Answer 5

• ~2 hours

_{Anesthesia Guidebook - Episode 18: Anesthesia Top Drawer Run Down - Part 2}

Question 6

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

Answer 6

• Metabolism: Liver (conjugation)
• Elimination: Kidneys

_{Anesthesia Guidebook - Episode 18: Anesthesia Top Drawer Run Down - Part 2}

Question 7

What is the ratio of alpha and beta blockade of an IV dose of labetalol?

Answer 7

• 1:7 alpha to beta