IBUTILIDE FUMARATE

Clinical safety rating: safe

Animal studies have demonstrated safety

How it works

Ibutilide fumarate is a Class III antiarrhythmic agent that prolongs the atrial and ventricular refractory period by blocking the rapid component of the delayed rectifier potassium current (IKr) and also enhances the slow inward sodium current (INa), resulting in prolongation of the action potential duration and effective refractory period.

What the body does with it

Metabolism	Extensively metabolized in the liver via oxidation, likely involving cytochrome P450 enzymes, with minimal renal excretion of unchanged drug.
Excretion	Primarily hepatic metabolism; less than 10% excreted unchanged in urine. Biliary/fecal excretion accounts for approximately 20% of total clearance.
Half-life	Terminal elimination half-life is 2–12 hours (mean 6 hours). In atrial fibrillation/flutter, the clinically effective half-life allowing for arrhythmia conversion is approximately 2–4 hours due to rapid redistribution.
Protein binding	Approximately 40% bound to plasma proteins, primarily albumin.
Volume of Distribution	Volume of distribution is approximately 11 L/kg, indicating extensive tissue distribution with rapid redistribution from cardiac tissue.
Bioavailability	Not available orally due to extensive first-pass metabolism; thus administered only intravenously. Bioavailability after IV administration is 100%.
Onset of Action	Intravenous: Onset of antiarrhythmic effect occurs within 1–10 minutes of starting infusion. Peak effect at 10–30 minutes after infusion completion.
Duration of Action	Duration of action is 1–2 hours for conversion of atrial fibrillation/flutter. Continuous ECG monitoring is required for at least 4 hours post-infusion due to risk of proarrhythmia (torsades de pointes), which can occur up to 4–6 hours after administration.

Classification & Brands

Dosing & administration

1 mg (10 mL of 0.1 mg/mL solution) IV infusion over 10 minutes; if arrhythmia persists after 10 minutes post-infusion, a second 1 mg dose may be administered. For patients weighing <60 kg, use 0.01 mg/kg.

Dosage form	INJECTABLE
Renal impairment	No specific dose adjustment is recommended based on GFR; however, use with caution in patients with renal impairment as elimination may be reduced.
Liver impairment	No specific dose adjustment for Child-Pugh class A or B; contraindicated in Child-Pugh class C (severe hepatic impairment).
Pediatric use	Safety and efficacy in pediatric patients have not been established; use is not recommended.
Geriatric use	No specific dose adjustment, but elderly patients may have increased sensitivity; consider lower initial dose and monitor for proarrhythmic effects due to age-related decreased clearance.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Other drugs that prolong the QT interval increase risk of torsades de pointes Can cause life-threatening ventricular arrhythmias particularly torsades de pointes.

Breastfeeding	Unknown if excreted in human milk. Due to potential for serious adverse reactions (e.g., cardiac arrhythmias) in nursing infants, discontinue breastfeeding or discontinue drug, considering importance to mother. M/P ratio not available.
Teratogenic Risk	Pregnancy Category C. Animal studies have shown fetal harm (increased fetal death, cardiovascular anomalies) at doses similar to human exposure. No adequate human studies. Avoid use in first trimester; use only if benefit outweighs risk in later trimesters.

Warnings & precautions

■ FDA Black Box Warning

Ibutilide can cause potentially fatal arrhythmias, particularly torsade de pointes. Patients should have continuous ECG monitoring during and for at least 4 hours after infusion. It should be administered only by personnel trained in ACLS in a setting with resuscitation equipment available.

Side Effect Profile

Common Effects	Headache
Serious Effects

Absolute Contraindications

["Known hypersensitivity to ibutilide","Baseline QT interval >440 msec (or >500 msec with conduction abnormalities)","History of polymorphic ventricular tachycardia (e.g., torsade de pointes)","Concurrent use of other drugs that prolong QT interval"]

Clinical Precautions

Precautions

["Risk of proarrhythmia (torsade de pointes, ventricular tachycardia)","Hypokalemia or hypomagnesemia should be corrected before administration","Use caution in patients with bradycardia, CHF, or reduced ejection fraction","Prolonged QT interval may increase risk","Renal or hepatic impairment may alter drug disposition"]

Clinical Tips & Counseling

Drug interactions

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