Class 2 antiarrhythmics (beta blockers) Flashcards
What are Class II antiarrhythmics?
Beta-adrenergic antagonists (beta blockers) that decrease sympathetic activity on the heart, reducing heart rate and contractility.
What is the mechanism of action of Class II antiarrhythmics?
They decrease cyclic AMP levels, reduce calcium influx, and prolong phase 4 of the nodal action potential, leading to decreased pacemaker activity and slowed AV nodal conduction.
How do beta blockers affect the nodal action potential?
They prolong phase 4 by reducing pacemaker current (If) through sodium channels, thereby decreasing spontaneous depolarization.
What is the effect of beta blockers on AV nodal conduction?
They prolong AV nodal conduction time and the effective refractory period, slowing ventricular response in supraventricular arrhythmias.
What are the primary indications for beta blockers?
Used for hypertension (not first line unless patient also has heart failure), angina, acute coronary syndromes (ACS), heart failure with reduced ejection fraction (HFrEF), atrial fibrillation/flutter for rate control, supraventricular tachycardia (SVT), migraine prophylaxis, thyrotoxicosis, variceal bleeding prophylaxis in cirrhosis, and glaucoma.
Which beta blockers are used for atrial fibrillation and atrial flutter?
Esmolol, metoprolol, propranolol (used for rate control).
Which beta blockers are used for supraventricular tachycardia (SVT)?
Esmolol (IV beta blocker, often used intraoperatively).
Which beta blocker is has the highest lipid solubility and why is this matter?
Propranolol, high solubility is good for migraine prophylaxis and essential tremor (due to CNS penetration).
Which beta blocker is used in the management of thyrotoxicosis?
Propranolol.
Which beta blocker is used for variceal bleeding prophylaxis in cirrhosis?
Nadolol.
Which beta blockers are preferred in patients with renal dysfunction (excreted by kidneys)?
Atenolol and Nadolol.
Which beta blocker is used in the treatment of glaucoma?
Timolol.
How are beta blockers classified based on receptor selectivity?
Cardioselective (β1-selective), Non-selective (β1 and β2), and Combined α and β antagonists.
Which beta blockers are cardioselective (β1-selective)?
Atenolol, bisoprolol, esmolol, metoprolol.
What is the mnemonic to remember cardioselective beta blockers?
“A through M” (e.g., Atenolol, Bisoprolol, Esmolol, Metoprolol), with the exception of labetalol, which is not cardioselective.
Which beta blockers are non-selective (β1 and β2)?
Labetalol, Propranolol, nadolol, timolol.
What is the mnemonic to remember non-selective beta blockers?
“N through Z” (e.g., Nadolol, Propranolol, Timolol), with the exception of labetalol, which is not cardioselective.
Which beta blockers have combined α and β antagonistic effects?
Carvedilol and labetalol.
Why should caution be used when prescribing beta blockers to patients with asthma or COPD?
Non-selective beta blockers can exacerbate bronchospasm; cardioselective beta blockers are preferred but still used with caution.
Why should beta blockers not be abruptly discontinued?
Abrupt withdrawal can lead to rebound tachycardia, hypertension, and exacerbation of angina.
What are common side effects of beta blockers?
- Fatigue
- Erectile dysfunction
- Depression
- Bradyarrhythmias
- Bronchospasm
- Potential masking of hypoglycemia symptoms
Why should beta blockers be used cautiously in diabetic patients?
They can mask hypoglycemic symptoms like tachycardia and may affect glucose metabolism.
When in toxic levels, which beta blockers can cause confusion and seizures?
Propanolol > Metoprolol = Labetalol = Carvedilol
What should be done immediately when beta blocker toxicity is suspected?
ECG
What is the treatment for beta blocker overdose?
Administration of fluids, atropine, and glucagon.
What is the effect of beta blockers on lipid profiles?
Some beta blockers, particularly those without intrinsic sympathomimetic activity, can cause mild hyperlipidemia.
