Beta Blockers

Question 1

What beta blockers can cause life threatening toxicology in overdose?

Answer 1

Sotalol and propranolol can be deadly, the rest can be managed with supportive care as they result in little/no toxicity

Question 2

What are risk factors that increase the risk of severe beta blocker toxicity?

Answer 2

Ingestion of propranolol/sotalol, underlying heart/lung disease, co-ingestion/regular treatment with CCB/digoxin, advancing age

Question 3

What is the threshold for severe propranolol toxicity?

Answer 3

As little as 1 gram

Question 4

What is an early ominous sign for beta blocker toxicity?

Answer 4

PR prolongation even in the absence of bradycardia

Question 5

Discuss the mechanism of action for beta blockers.

Answer 5

Competitive antagonists at beta-1 and beta-2 receptors; leads to decreased intracellular cAMP concentration. This in turn leads to blunting of metabolic, chronotropic, inotropic effects of catecholamines

Question 6

Discuss the mechanism of action of propranolol.

Answer 6

Beta-1/beta-2 receptor antagonist + sodium-channel blocker (class 1 effects). Also is lipid-soluble so enters the CNS where is exerts direct toxicity.

Question 7

Discuss the mechanism of action of sotalol.

Answer 7

Beta-1/beta-2 receptor antagonism + blocks cardiac K+ channels (class 3 effects)

Question 8

What are the ECG findings in a patient taking propranolol in overdose.

Answer 8

QRS widening and ventricular dysrhythmias in addition to the standard beta blocker effects

Question 9

What are the ECG findings in a patient taking sotalol in overdose?

Answer 9

QT prolongation in addition to the tandard beta blocker effects

Question 10

What is the biggest difference between beta blockers and propranolol?

Answer 10

Propranolol is very lipophilic

Question 11

When do you anticipate manifestations of beta-blocker overdose?

Answer 11

Withhin 4 hours manifested by a fall in HR

Question 12

Describe the manifestations of beta-blocker toxicity.

Answer 12

Cardiac: hypotension, brady (dysrhythmias), QRS/QT prolongation in specific agents. CNS: delirium, coma, seizures. Other: bronchospasm, APO, hyperkalaemia, hypo/hyperglycaemia

Question 13

What beta-blocker causes QRS prolongation?

Answer 13

Propranolol

Question 14

What beta-blocker causes QT prolongation?

Answer 14

Sotalol which may progress to torsades

Question 15

What beta-blocker can cause seizures?

Answer 15

Propranolol

Question 16

How is a propranolol overdose best managed?

Answer 16

Like a TCA overdose with sodium bicarbonate

Question 17

What are four crucial drugs to give in beta-blocker overdose?

Answer 17

Atropine 0.01-0.03 mg/kg IV, isoprenaline 4 mcg/min IV infusion, adrenaline, high-dose insulin

Question 18

What are three things to do for torsades in sotalol overdose?

Answer 18

Isoprenaline, magnesium and overdrive pacing

Question 19

Compare sotalol and propranolol in overdose.

Answer 19

Sotalol: K+ channel effects leads to QT prolongation. Propranolol: Na+ channel effects leads to QRS widening + CNS depression/coma/seizures