BRETYLIUM TOSYLATE

BRETYLIUM TOSYLATE
(bre-til'ee-um)
Classifications: antiarrhythmic, class iii;
Therapeutic: antiarrhythmic, class iii

Prototype: Amiodarone
Pregnancy Category: C

Availability

2 mg/mL, 4 mg/mL, 50 mg/mL injection

Action

Suppresses ventricular fibrillation by direct action on the myocardium and ventricular tachycardia by adrenergic blockade. Shortly after administration, norepinephrine is released from adrenergic postganglionic nerve terminals, resulting in a moderate increase in BP, heart rate, and ventricular irritability. Subsequently (1–2 h), drug-induced release and reuptake of norepinephrine are blocked, leading to a state resembling surgical sympathectomy.

Therapeutic Effect

Suppresses arrhythmias with a reentry mechanism and decreases dispersion of ectopic foci. PR, QT, and QRS intervals are unchanged. Because onset of desired action is delayed, bretylium is not a first-line antiarrhythmic agent.

Uses

Short-term prophylaxis and treatment of ventricular fibrillation; life-threatening arrhythmias such as ventricular fibrillation not responsive to conventional therapy [e.g., lidocaine, procainamide, direct current (cardioversion)].

Contraindications

No contraindications for use in life-threatening refractory ventricular arrhythmias; digitalis toxicity; pregnancy (category C).

Cautious Use

Digitalis-induced arrhythmias, patients with fixed cardiac output (e.g., severe aortic stenosis or severe pulmonary hypertension because profound hypotension may result), sinus bradycardia, patients on digitalis maintenance, angina pectoris, impaired renal function, renal disease; lactation.

Route & Dosage

Ventricular Fibrillation
Adult: IV 5 mg/kg rapid IV injection, may increase to 10 mg/kg and repeat q15–30 min (max: 30 mg/kg/d); may also give by continuous infusion at 1–2 mg/min IM 5–10 mg/kg, may repeat in 1– 2 h if arrhythmia persists, then 5–10 mg/kg q6–8h for maintenance
Child: IV 5 mg/kg, may repeat 15–30min (max: 30 mg/kg) IM 2–5 mg/kg as single dose

Administration

Limit use to patients in facilities adequately equipped and staffed for constant monitoring of ECG and BP and for cardiovascular/pulmonary resuscitation and cardioversion.

Intramuscular
  • Administer no more than 5 mL in any one IM site.
  • Keep a record of injection sites. Injection into same site can cause muscle atrophy, necrosis, and fibrosis.
Intravenous
  • IV administration to infants and children: Verify correct IV concentration and rate of infusion/injection with physician.

PREPARE: Direct: Give undiluted.  Intermittent: Give diluted in 50 mL or more of NS or D5W.  

ADMINISTER: Direct: Give undiluted at a rate of 1 dose/15 seconds.  Intermittent: Give diluted at a rate of 1–2 mg/min.  

INCOMPATIBILITIES Solution/additive: Dobutamine, pantoprazole phenytoin, procainamide. Y-site: Amphotericin B, cholestryl, propofol, warfarin.

  • Store at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

CV: Both supine and postural hypotension with dizziness, vertigo, lightheadedness, faintness, syncope, transitory hypertension, bradycardia, increased frequency of PVCs, exacerbation of digitalis-induced arrhythmias. GI: Nausea, vomiting (particularly with rapid IV). Respiratory: Respiratory depression.

Diagnostic Test Interference

Urinary VMA, epinephrine, and norepinephrine levels may be decreased during bretylium therapy.

Interactions

Drug: Lidocaine, procainamide, quinidine, propranolol may antagonize antiarrhythmic effects and compound hypotension; antihypertensive agents will add to hypotensive effects; digitalis glycosides may worsen arrhythmias through digitalis toxicity. MACROLIDES, QUINOLONES increase the risk of arrhythmias.

Pharmacokinetics

Onset: Minutes after IV; up to 6 h IM. Peak: 6–9 h. Duration: 6–24 h. Distribution: Does not cross blood–brain barrier; not known if crosses placenta or distributed into breast milk. Metabolism: Not metabolized. Elimination: 70–80% in urine in 24 h. Half-Life: 4–17 h.

Nursing Implications

Assessment & Drug Effects

  • Anticipate vomiting. IV administration is associated with a high incidence of nausea and vomiting. These side effects can be minimized by slow administration of drug (≥10 min).
  • Establish baseline readings and monitor BP and ECG when drug is administered. Observe for initial transient rise in BP, increased heart rate, PVCs and other arrhythmias, or worsening of existing arrhythmias, which may occur within a few minutes to 1 h after drug administration. Keep physician informed. Initial effect of hypertension is usually followed within 1 h by a fall in supine BP and by orthostatic hypotension.
  • Use supine position until patient develops tolerance to hypotensive effect of bretylium (generally in several days). Hypotension can occur in the supine position, particularly in patients with severely compromised cardiac function. It may not readily respond to therapy (e.g., vasopressors, fluids); early reporting is essential.
  • Raise or lower head of bed slowly; advise patient to make position changes slowly in order to prevent orthostatic hypotension.
  • Monitor I&O, particularly in patients with impaired renal function.

Patient & Family Education

  • Make position changes slowly. If allowed to be out of bed, dangle legs for a few minutes before standing, but do not stand still for prolonged periods. Men should sit on toilet to urinate.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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