Skip to Main Content

++

  1. Pharmacology. Propranolol is a nonselective beta-adrenergic blocker that acts on beta1 receptors in the myocardium and beta2 receptors in the lung, vascular smooth muscle, and kidney. Within the myocardium, propranolol depresses the heart rate, conduction velocity, myocardial contractility, and automaticity. Although propranolol is effective orally, for toxicologic emergencies it usually is administered by the intravenous route. After intravenous injection, the onset of action is nearly immediate and the duration of effect is 10 minutes to 2 hours, depending on the cumulative dose. The drug is eliminated by hepatic metabolism, with a half-life of about 2–3 hours. Propranolol also has antagonistic properties at the serotonin (5-HT1A) receptor and has been used to treat serotonin syndrome with mixed success (anecdotal case reports).

  2. Indications

    1. To control excessive sinus tachycardia or ventricular arrhythmias caused by catecholamine excess (eg, theophylline or caffeine), sympathomimetic drug intoxication (eg, amphetamines, pseudoephedrine, or cocaine), excessive myocardial sensitivity (eg, chloral hydrate, freons, or chlorinated and other hydrocarbons), or thyrotoxicosis.

    2. To control hypertension in patients with excessive beta1-mediated increases in heart rate and contractility; used in conjunction with a vasodilator (eg, phentolamine) in patients with mixed alpha- and beta-adrenergic hyperstimulation.

    3. To raise diastolic blood pressure in patients with hypotension caused by excessive beta2-mediated vasodilation (eg, theophylline or metaproterenol).

    4. May ameliorate or reduce beta-adrenergic–mediated electrolyte and other metabolic abnormalities (eg, hypokalemia, hyperglycemia, and lactic acidosis).

    5. Serotonin syndrome (See Hyperthermia).

  3. Contraindications

    1. Use with extreme caution in patients with asthma, congestive heart failure, sinus node dysfunction, or another cardiac conduction disease and in those receiving calcium antagonists and other cardiac-depressant drugs.

    2. Do not use as a single therapy for hypertension resulting from sympathomimetic overdose. Propranolol produces peripheral vascular beta blockade, which may abolish beta2-mediated vasodilation and allow unopposed alpha-mediated vasoconstriction, resulting in paradoxical worsening of hypertension; coronary artery constriction may cause or exacerbate acute coronary syndrome.

  4. Adverse effects

    1. Bradycardia and sinus and atrioventricular block.

    2. Hypotension and congestive heart failure.

    3. Bronchospasm in patients with asthma or bronchospastic chronic obstructive pulmonary disease. Note: Propranolol (in small intravenous doses) has been used successfully in patients with asthma overdosed on theophylline or beta2 agonists without precipitating bronchospasm.

    4. Use in pregnancy. FDA Category C (first trimester) and Category D (second and third trimesters). Propranolol may cross the placenta, and neonates delivered within 3 days of administration of this drug may have persistent beta-adrenergic blockade. However, this does not preclude its acute, short-term use in a seriously symptomatic patient (See Introduction in Section III).

  5. Drug or laboratory interactions

    1. Propranolol may allow unopposed alpha-adrenergic stimulation in patients with mixed adrenergic stimulation (eg, epinephrine surge in patients with acute hypoglycemia, pheochromocytoma, or cocaine or amphetamine intoxication), resulting in severe hypertension or end-organ ischemia.

    2. Propranolol has an additive hypotensive effect with other antihypertensive agents.

    3. This drug may potentiate competitive neuromuscular blockers (See Neuromuscular Blockers).

    4. Propranolol has additive depressant effects on cardiac conduction and contractility when given with calcium antagonists.

    5. Cimetidine reduces hepatic clearance of propranolol.

    6. Propranolol may ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.