Ibutilide

Classification:

Class III – Potassium (K⁺) channel blockers

Amiodarone – the most effective anti-arrhythmic drug, but associated with the highest rate of adverse effects.
Dronedarone – similar to amiodarone, but less potent and associated with fewer adverse effects.
Sotalol – also a non-selective beta-blocker.
Ibutilide – may be used for acute cardioversion of pre-excited atrial fibrillation (AF).

$Diagram of the effect of ibutilide as a class III antiarrhythmic illustrating prolongation of the effective refractory period of an accessory pathway and pharmacological cardioversion of preexcited atrial fibrillation to sinus rhythm.$

Mechanism:

Reduces excitability and automaticity and prevents re-entry in atrial and ventricular myocardium

by inhibiting K⁺ channels and partially late Na⁺ channels
Prolongs the non-nodal action potential (AP) and effective refractory period (ERP)

Accessory pathway – prolongs ERP
Almost no effect on the SA node

Effect:

Cardioversion of AF to sinus rhythm – termination of an atrial fibrillation (AF) episode and restoration of sinus rhythm
Cardioversion of pre-excited AF to sinus rhythm
Cardioversion of atrial flutter (AFL) to sinus rhythm – termination of an AFL episode and restoration of sinus rhythm

Ibutilide is the most effective anti-arrhythmic drug for acute conversion of AFL

Ibutilide and atrial fibrillation (AF)
Brand name
Convert
Indications
Acute cardioversion of AF to sinus rhythm May also be used in pre-excited AF (AF with delta wave on ECG) Acute cardioversion of AFL to sinus rhythm
Dosing
Acute cardioversion of AF to sinus rhythm (intravenous) (< 60 kg): 0.01 mg/kg administered over 10 minutes (> 60 kg): 1 mg administered over 10 minutes A second identical dose administered over 10 minutes may be given after 10 minutes if conversion to sinus rhythm has not occurred
Onset of action
30–90 minutes
Effect
Time to conversion to sinus rhythm and success rate 30–90 minutes – 30–50 % (intravenous) – in AF < 60 minutes – 60–75 % (intravenous) – in AFL
Duration of action
4–6 hours (intravenous)
Contraindications
Hypotension (systolic < 100 mmHg) Bradycardia (< 50/min.) Prolonged QT interval (QTc > 440 ms) Long QT syndrome Cardiogenic shock Decompensated heart failure Severe electrolyte imbalance (especially hypokalaemia, hypomagnesaemia) Allergy to ibutilide

Patient monitoring during ibutilide administration:

Stop administration if a reason for infusion discontinuation occurs (see table below).

Patient monitoring during ibutilide administration
Monitoring period	What to monitor	Reason for discontinuation
During infusion (0–10 minutes)	ECG (QTc interval) Blood pressure	QTc > 500 ms Torsades de pointes Bradycardia < 40/min. Hypotension < 90/60 mmHg
30–120 minutes after administration	ECG Blood pressure	QTc > 500 ms Arrhythmias

Adverse effects:

Common (1–10 %):

Ventricular arrhythmias
AV block
Bundle branch block
Hypotension
Bradycardia
QT interval prolongation
Headache
Nausea

Rare (< 1 %)

Bullous rash

Vernakalant and ibutilide are intravenous anti-arrhythmic drugs indicated for pharmacological cardioversion of AF.

They belong to different classes and their main properties differ partially.

Ibutilide vs vernakalant and atrial fibrillation
Property	Ibutilide	Vernakalant
Class	Class III – K⁺ channel blocker	“Other anti-arrhythmic” (blocks Na⁺ and K⁺ channels)
Mechanism of action	Acts on atria, ventricles, and accessory pathways	Acts only on atria
Indication	Acute intravenous cardioversion of AF and flutter	Acute intravenous cardioversion of AF
Use in pre-excited AF	Yes	Contraindicated
Use in atrial flutter	Yes	No
Conversion success rate to sinus rhythm	~30–50 % (AF), ~60–75 % (AFL)	~50–70 % (AF)
Adverse effects	QT prolongation, torsades de pointes	Hypotension, bradycardia, dysgeusia, paraesthesia