Disopyramide

Classification:

Procainamide – mainly used in patients with pre-excited atrial fibrillation (AF).
Disopyramide – due to its vagolytic effect, suitable in vagal AF.

Mechanism:

Slows conduction velocity and reduces excitability in atrial and ventricular myocardium

Prolongs the effective refractory period (ERP) in atrial and ventricular myocardium

Also partially blocks potassium channels (therefore exhibits Class III properties), thus prolonging ERP

Effect on AF:

Maintenance of sinus rhythm – prevents recurrence of vagal atrial fibrillation (AF)

Disopyramide and atrial fibrillation (AF)
Brand names
Disopyramide, Disopiramida, Disopyramidum, Dirytmin, Durbis, Rythmodan
Indications
Maintenance of sinus rhythm – in vagal AF
Dosing
Chronic rhythm control – maintenance of sinus rhythm (oral) 100–150 mg three times daily – immediate-release formulation 200–250 mg twice daily – prolonged-release formulation
Onset of action
< 4 hours (oral)
Effect
Maintenance of sinus rhythm (paroxysmal or persistent AF) at 1 year 25–35 %
Duration of action
6–8 hours (oral) – immediate-release 12–24 hours (oral) – prolonged-release
Contraindications
Second- or third-degree AV block (without pacemaker) Prolonged QTc interval > 500 ms History of torsades de pointes Severe heart failure / cardiogenic shock (disopyramide has a negative inotropic effect) Myasthenia gravis Narrow-angle glaucoma Urinary retention, severe prostatic hyperplasia, ileus (disopyramide has a strong anticholinergic effect) Severe renal or hepatic impairment (without dose adjustment) Allergy to disopyramide

Patient monitoring during disopyramide therapy:

Discontinue or reduce the dose if adverse effects occur or if a reason for discontinuation appears (see table below).

Patient monitoring after initiation of disopyramide
Time from initiation	What to monitor	Reason for treatment discontinuation
Week 1	ECG (QTc, QRS) Renal function, electrolytes (K⁺, Mg²⁺) Anticholinergic symptoms	QTc > 500 ms QRS widening > 25% Anticholinergic symptoms Arrhythmias (torsades de pointes) Electrolyte or renal impairment
3 months	ECG (QTc, QRS) Renal function, electrolytes (K⁺, Mg²⁺) Anticholinergic symptoms	QTc > 500 ms QRS widening > 25% Anticholinergic symptoms Arrhythmias (torsades de pointes) Electrolyte or renal impairment
6–12 months	Echocardiography Long-term treatment tolerance	Ejection fraction < 40 % Poor tolerance or lack of treatment efficacy

Adverse effects:

Anticholinergic symptoms (dry mouth, urinary retention, constipation, blurred vision, mydriasis, worsening of glaucoma)

Disopyramide and procainamide belong to Class IA anti-arrhythmic drugs but have different properties.

The main feature of disopyramide is its pronounced vagolytic effect, making it suitable for vagal AF.

Disopyramide vs Procainamide and atrial fibrillation
Property	Disopyramide	Procainamide
Class	IA + anticholinergic (vagolytic) effect	IA (Na⁺ channel blocker)
Route of administration	Oral (chronic prevention of recurrences)	Intravenous (acute conversion of AF, especially with WPW)
Pre-excited AF (WPW)	No – not suitable	Yes – effective and safe
Vagal AF	Yes – first-line drug, suppresses vagal tone	Neutral effect, no vagolytic activity
Maintenance of sinus rhythm	Effective mainly in vagal AF	No – not used for long-term therapy
Main risks	QT prolongation, torsades de pointes, anticholinergic adverse effects (dry mouth, urinary retention)	Hypotension, QT prolongation, lupus-like syndrome