bretylium (Rx)

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Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

solution for injection

  • 500mg/10mL (50mg/mL single-dose vial)

Ventricular Arrhythmia

Indicated for prophylaxis and treatment of ventricular fibrillation (VF); also indicated for treatment of life-threatening ventricular arrhythmias (eg, ventricular tachycardia [VT] unresponsive to first-line antiarrhythmic agents [eg, lidocaine])

Immediately life-threatening ventricular arrhythmias (eg, VF, unstable VT)

  • Other usual cardiopulmonary resuscitative procedures, including electrical cardioversion, should be used prior to and following the injection in accordance with good medical practice
  • Undiluted solution: 5 mg/kg IV by rapid injection; if arrhythmia persists, may increase dose to 10 mg/kg and repeat prn
  • Diluted solution for continuous suppression: 1-2 mg/min IV; alternatively, 5-10 mg/kg IV over at least 8 min q6hr

Other ventricular arrhythmias

  • IV
    • Use diluted solution
    • 5-10 mg/kg IV over at least 8 min; may repeat dose at 1- to 2-hr intervals if arrhythmia persists
    • Maintenance: 5-10 mg/kg IV over at least 8 min q6hr; alternatively, 1-2 mg/min IV continuous infusion
  • IM
    • Use undiluted solution
    • 5-10 mg/kg IM; may repeat dose at 1- to 2-hr intervals if arrhythmia persists
    • Maintenance: 5-10 mg/kg IM q6-8hr
    • Switch of oral antiarrhythmic agent as soon as possible for continued maintenance therapy

Dosage Modifications

Renal impairment

  • Primarily excreted via kidneys; increase dosage interval in patients with impaired renal function
  • Removed by hemodialysis

Dosing Considerations

Limit use to intensive care units, coronary care units, or other facilities where equipment and personnel for constant monitoring of cardiac arrhythmias and blood pressure are available

Following administration, onset of antiarrhythmic action may occur between 20 minutes and 2 hr; although, it appears to act within minutes in VF; delay in effect appears to be longer after IM than after IV injection

Dosage Modifications

Renal impairment

  • Primarily excreted via kidneys; increase dosage interval in patients with impaired renal function
  • Removed by hemodialysis

Dosing Considerations

Drug is substantially excreted by the kidneys, carefully select dose for geriatric patients; consider monitoring renal function

Limit use to intensive care units, coronary care units, or other facilities where equipment and personnel for constant monitoring of cardiac arrhythmias and blood pressure are available

Following administration, onset of antiarrhythmic action may occur between 20 minutes to 2 hr; although, it appears to act within minutes in ventricular fibrillation; delay in effect appears to be longer after IM than after IV injection

Safety and efficacy not established

Ventricular Arrhythmia

Indicated for prophylaxis and treatment of ventricular fibrillation (VF); also indicated for treatment of life-threatening ventricular arrhythmias (eg, ventricular tachycardia [VT] unresponsive to first-line antiarrhythmic agents [eg, lidocaine])

In general, dose selection for geriatric patients should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or drug therapy

Risk of orthostatic hypotension exists, particularly if administered IV at rate exceeding recommendations

Immediately life-threatening ventricular arrhythmias (eg, VF, unstable VT)

  • Other usual cardiopulmonary resuscitative procedures, including electrical cardioversion, should be used prior to and following the injection in accordance with good medical practice
  • Undiluted solution: 5 mg/kg IV by rapid injection; if arrhythmia persists, may increase dose to 10 mg/kg and repeat prn
  • Diluted solution for continuous suppression: 1-2 mg/min IV; alternatively, 5-10 mg/kg IV over at least 8 min q6hr

Other ventricular arrhythmias (IV)

  • Use diluted solution
  • 5-10 mg/kg IV over at least 8 min; may repeat dose at 1- to 2-hr intervals if arrhythmia persists
  • Maintenance: 5-10 mg/kg IV over at least 8 min q6hr; alternatively, 1-2 mg/min IV continuous infusion

Other ventricular arrhythmias (IM)

  • Use undiluted solution
  • 5-10 mg/kg IM; may repeat dose at 1- to 2-hr intervals if arrhythmia persists
  • Maintenance: 5-10 mg/kg IM q6-8hr
  • Switch of oral antiarrhythmic agent as soon as possible for continued maintenance therapy

Dosing Considerations

Drug is substantially excreted by the kidneys; carefully select dose for geriatric patients; consider monitoring renal function

Limit use to intensive care units, coronary care units, or other facilities where equipment and personnel for constant monitoring of cardiac arrhythmias and blood pressure are available

Following administration, onset of antiarrhythmic action may occur between 20 minutes and 2 hr; although, it appears to act within minutes in VF; delay in effect appears to be longer after IM than after IV injection

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Interactions

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            Adverse Effects

            >10%

            Hypotension, some degree even while supine (50%)

            <1%

            ~0.7%

            • Vertigo
            • Dizziness
            • Lightheadedness
            • Syncope

            ~0.2%

            • Increased frequency of premature ventricular contractions
            • Transitory hypertension
            • Initial increase in arrhythmias
            • Precipitation of anginal attacks
            • Sensation of substernal pressure

            ~0.1%

            • Renal dysfunction
            • Diarrhea, abdominal pain
            • Hiccups
            • Erythematous macular rash
            • Flushing
            • Hyperthermia
            • Confusion, paranoid psychosis, emotional lability, anxiety
            • Lethargy
            • Generalized tenderness
            • Shortness of breath, diaphoresis, nasal stuffiness
            • Mild conjunctivitis
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            Warnings

            Contraindications

            Digitalis-induced arrhythmias

            Cautions

            Hypotension

            • Administration regularly results in postural hypotension, subjectively recognized by dizziness, lightheadedness, vertigo, or faintness
            • Some degree of hypotension is present in ~50% of patients while they are supine
            • Hypotension may occur at doses lower than those needed to suppress arrhythmias
            • Keep patients in supine position until tolerance to hypotensive effect develops; tolerance occurs unpredictably, but may be present after several days
            • Patients aged >65 years may be at increased risk of developing orthostatic hypotension, especially if recommended IV infusion exceeded
            • Hypotension with supine systolic pressure >75 mm Hg need not be treated unless there are associated symptoms
            • If supine systolic pressure falls below 75 mm Hg, dopamine or norepinephrine infusion may be used to raise blood pressure
            • When catecholamines are administered, use a dilute solution and closely monitor blood pressure (pressor effects catecholamines enhanced by bretylium)
            • Volume expansion with blood or plasma and correction of dehydration should be carried out where appropriate

            Transient hypertension

            • Bretylium causes an initial norepinephrine release from adrenergic postganglionic nerve terminals
            • Transient hypertension or increased frequency of premature ventricular contractions and other arrhythmias may occur in some patients, especially after too vigorous a dosing

            Fixed cardiac output

            • Avoid use in patients with fixed cardiac output (eg, severe aortic stenosis or pulmonary hypertension) since severe hypotension may result from a fall in peripheral resistance without a compensatory increased cardiac output
            • If survival is threatened by the arrhythmia, bretylium may be used, but vasoconstrictive catecholamines should be given promptly if severe hypotension occurs

            Hyperthermia

            • Hyperthermia, characterized by temperature excess of 106°F, reported; temperature rise can begin within 1 hr or later after administration and peak within 1-3 days
            • If suspected or diagnosed, discontinue bretylium and institute treatment immediately

            Drug interaction overview

            • Digoxin
              • Initial release of norepinephrine caused by bretylium may aggravate digitalis toxicity
              • When a life-threatening cardiac arrhythmia occurs in a digitalized patient, bretylium should be used only if the etiology of the arrhythmia does not appear to be digitalis toxicity and other antiarrhythmic drugs are not effective
              • Avoid simultaneous initiation of therapy with digitalis glycosides and bretylium
            • Monoamine oxidase inhibitors (MAOIs)
              • Bretylium produces release of catecholamines from nerve endings
              • This increased catecholamine release is potentiated by MAOIs
            • Catecholamines
              • If catecholamines (ie, dopamine, norepinephrine) are administered to treat systolic blood pressure <75 mm Hg, a dilute solution should be used and blood pressure monitored closely because the pressor effects of the catecholamines are enhanced by bretylium
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            Pregnancy & Lactation

            Pregnancy

            Unknown whether bretylium can cause fetal harm when administered to pregnant women or can affect reproduction capacity

            Administer during pregnancy only if clearly needed

            Animal reproduction studies have not been conducted

            Lactation

            Data are not available

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.

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            Pharmacology

            Mechanism of Action

            Accumulates in sympathetic ganglia and their postganglionic adrenergic neurons when administered slowly or incrementally, where it inhibits norepinephrine release by depressing adrenergic nerve terminal excitability

            Also suppresses ventricular fibrillation (VF) and ventricular arrhythmias; mechanisms of antifibrillatory and antiarrhythmic actions are not established, although electrophysiologic actions have been described in animal studies

            Electrophysiologic effects observed in animal studies

            • Increased VF threshold
            • Increased action potential duration and effective refractory period without changes in heart rate
            • Little effect on the rate of rise or amplitude of the cardiac action potential (Phase 0) or in resting membrane potential (Phase 4) in normal myocardium; however, when cell injury slows the rate of rise, decreases amplitude, and lowers resting membrane potential, bretylium transiently restores these parameters toward normal
            • In canine hearts with infarcted areas, bretylium decreases disparity in action potential duration between normal and infarcted regions
            • Increased impulse formation and spontaneous firing rate of pacemaker tissue, as well as increased ventricular conduction velocity

            Absorption

            Onset of action: 20 minutes to 2 hr

            Elimination

            Half-life: 6-10 hr (normal renal function)

            Excretion: Urine (80% within 24 hr; additional 10% within 96 hr)

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            Administration

            IV Compatibility

            D5W

            0.9% NaCl

            IV Preparation

            Solution should appear clear; slight discoloration does not alter potency

            Rapid IV bolus: Do NOT dilute solution

            Continuous or intermittent IV infusion: Dilute 500 mg to a minimum of 50 mL with D52 or 0.9% NaCl

            IM Preparation

            Solution should appear clear; slight discoloration does not alter potency

            Do NOT dilute solution

            IV Administration

            Patients should remain in supine position until tolerance to the hypotensive effect of bretylium develops; tolerance occurs unpredictably but may be present after several days

            Immediately life-threatening ventricular arrhythmias

            • Rapid IV bolus (undiluted drug): When used for immediately life-threatening ventricular arrhythmias (eg, VF, hemodynamically unstable VT), give rapid IV bolus and if continuous suppression needed, follow with continuous or intermittent IV infusion (dilute drug as described above)
            • Continuous IV solution infusion: 1-2 mg/min
            • Intermittent IV infusion: 5-10 mg/kg infused over at least 8 min q6hr
            • Rapid infusion
              • More rapid infusion may cause nausea and vomiting, and possibly provoke hypertensive crisis
              • May increase orthostatic hypotension risk, especially in patients aged ≥65 yr

            IM Administration

            Patients should be kept in supine position until tolerance to the hypotensive effect of bretylium develops; tolerance occurs unpredictably but may be present after several days

            Do not dilute for IM injection

            Do not inject directly into or near a major nerve

            Rotate injection site if repeated

            Do not exceed 5 mL/injection site

            As soon as possible, and when indicated, change to oral antiarrhythmic agent for maintenance therapy

            Storage

            Store at 20-25°C (68-77°F)

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            Formulary

            FormularyPatient Discounts

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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
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            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.