Pharmacology of β Agonists in Heart Failure

Dobutamine in CHF Management

• Dobutamine is the β agonist of choice for managing patients with systolic dysfunction and congestive heart failure (CHF).
• The primary hemodynamic effect of dobutamine is to increase stroke volume, which it achieves through its positive inotropic action.

Sympathomimetics and Sympatholytics

Synthesis, Release, and Metabolism of Catecholamine

• Not actually sympathetic drugs but produce sympathomimetic-like effect

Direct Acting Nonselective Agonists

• Epinephrine (adrenaline): α and β agonist, potent vasoconstrictor and cardiac stimulant
• Isoproterenol: nonselective β agonist
• Oxymetazoline: nonselective α agonist, used as topical decongestant

Direct Acting Selective Adrenergic Receptor Agonists

• Terbutaline, Albuterol (Salbutamol): selective β2 agonist, bronchodilator
• Dobutamine: selective β1 agonist, used for management of patients with systolic dysfunction and CHF
• Phenylephrine: selective α1 receptor agonist
• Clonidine: selective α2 agonist, used primarily for systemic hypertension

Selective β1 Adrenergic Receptor Antagonists

• Atenolol: very hydrophilic, incompletely absorbed, and excreted largely unchanged in urine
• Metoprolol: almost completely absorbed, half-life 3-4 hours
• Esmolol: very short duration of action, administered intravenously
• Bisoprolol: highly selective β1 antagonist, generally well tolerated

α/β Antagonists/Blockers

• Labetalol: blocks β1, β2, and α1 receptors, has membrane stabilizing activity
• Carvedilol: blocks β1, β2, and α1 receptors, has antioxidant and anti-proliferative effects

Therapeutic Uses of β Blockers

• Cardiovascular diseases: hypertension, angina, acute coronary syndromes, supraventricular and ventricular arrhythmias, myocardial infarction
• Congestive Heart Failure: chronic administration is efficacious in prolonging life in the therapy of heart failure
• Glaucoma: β-receptor antagonists are useful in the treatment of chronic open-angle glaucoma
• Hyperthyroidism: β-blockers control many of the cardiovascular signs and symptoms
• Migraine: Propranolol, timolol, and metoprolol are used for prophylaxis

α Receptor Blockers

• Reversible antagonists: Phentolamine and prazosin
• Irreversible antagonists: Phenoxybenzamine covalently binds to α-receptors, resulting in irreversible blockade

Nonselective α Blockers

• Phenoxybenzamine: blocks α1 and α2 receptors, irreversibly in smooth muscle and other sites

This quiz covers the use of β agonists, specifically dobutamine, in the management of patients with systolic dysfunction and chronic heart failure (CHF). It explores the principal hemodynamic effects of dobutamine on stroke volume.