Class Ia antiarrhythmic Pregnancy: Safety in human pregnancy not established; reported to stimulate contractions of the pregnant uterus. Use only if benefits clearly outweigh possible risks to mother and foetus. Secreted in breast milk - use in lactation only if essential, with close infant supervision.

Disopyramide

Brand names: Rythmodan, Norpace

Disopyramide is a class Ia antiarrhythmic used in the treatment of certain ventricular and supraventricular arrhythmias.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 300 mg to 800 mg daily in divided doses

Route: Oral

Frequency: In divided doses

Elderly (especially elderly non-smokers): consider a dose reduction owing to reduced renal and hepatic function. Safety and efficacy in children under 18 years not established. Treatment of life-threatening or haemodynamically significant arrhythmias must be initiated in hospital. Avoid in patients with glaucoma; measure intraocular pressure before treatment in those with a history/family history of glaucoma. Use with caution in significant cardiac failure (negative inotropic effect) - patients should be fully digitalised or otherwise controlled beforehand.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or excipients
Unpaced second- or third-degree atrioventricular block
Bundle-branch block associated with first-degree atrioventricular block; unpaced bifascicular block
Pre-existing long QT syndromes
Severe sinus node dysfunction
Severe heart failure (unless secondary to cardiac arrhythmia)
Concomitant administration with other anti-arrhythmics or other drugs liable to provoke ventricular arrhythmias, especially Torsade de pointes

Side effects

Proarrhythmia: QT prolongation, QRS widening, AV block, bundle-branch block; ventricular tachycardia, ventricular fibrillation, Torsade de pointes
Atropine-like (anticholinergic) effects: dry mouth, urinary retention/dysuria, constipation, paralytic ileus (especially elderly), accommodation disorders, diplopia
Severe heart failure or cardiogenic shock with hypotension, renal insufficiency and/or acute hepatic ischaemia
Hypoglycaemia, sometimes severe (rare) - in some cases resulting in coma
Neutropenia (very rare); agranulocytosis (not known)

Interactions

Other anti-arrhythmics or other drugs liable to provoke ventricular arrhythmias (especially Torsade de pointes): contraindicated (see section 4.5)

Clinical monograph

How it works

It blocks cardiac fast sodium channels to slow conduction and prolong the action potential, and additionally has marked anticholinergic and negative inotropic properties.

Prescribing in practice

It prolongs the QT interval and can be pro-arrhythmic, including torsade de pointes, so avoid in significant QT prolongation and with other QT-prolonging drugs.
Its negative inotropic effect means it should be avoided in heart failure and significant left ventricular dysfunction.
Pronounced antimuscarinic effects can cause urinary retention, dry mouth and worsen glaucoma, so use cautiously where these are a concern.

Monitoring

Monitor the ECG including QT interval, with attention to heart failure symptoms and anticholinergic effects.

Counselling the patient

Report palpitations, fainting or marked dizziness.
Expect possible dry mouth, blurred vision or difficulty passing urine.
Tell your clinician about other heart-rhythm or QT-affecting medicines.

Evidence & guidelines

Class Ia antiarrhythmics carry a recognised pro-arrhythmic risk, and use of these older agents has declined in line with safety evidence from antiarrhythmic outcome studies.

Reference: SmPC Rythmodan; ESC HCM Guidelines 2023; ESC AF Guidelines 2024; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways