Class Ic antiarrhythmic Pregnancy: No adequate and well-controlled studies in pregnant women; use during pregnancy only if the potential benefit justifies the potential risk to the foetus. Crosses the placenta (umbilical cord concentration about 30% of maternal blood). Excretion in human breast milk not studied but limited data suggest it may be excreted — use with caution in nursing mothers.

Propafenone hydrochloride

Brand names: Arythmol

Propafenone is a class Ic antiarrhythmic with weak beta-blocking properties, used for paroxysmal atrial fibrillation and certain other supraventricular and ventricular 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: Initially 150 mg

Route: Oral (film-coated / sugar-coated tablets — swallow whole, without chewing, with liquid)

Frequency: Three times daily initially; increase at a minimum of three-day intervals to 300 mg twice daily, and if necessary further

Max: 300 mg three times daily

Therapy should be initiated under hospital conditions by a physician experienced in the treatment of arrhythmias. The individual maintenance dose should be determined under cardiological surveillance including ECG monitoring and blood pressure control. If the QRS interval is prolonged by more than 20%, the dose should be reduced or discontinued until the ECG returns to normal limits. Dose increases should not be attempted until the patient has been receiving treatment for three to four days. A reduction in the total daily dose is recommended for patients below 70 kg bodyweight. Elderly: treatment should be initiated gradually and with particular caution in small incremental doses (same for maintenance); any dose increases should not be undertaken until after five to eight days of therapy; monitor carefully. Paediatric population: a suitable dosage form for children is not available (per SPC) — no paediatric regimen stated. Tablets must be swallowed whole owing to the bitter taste and surface anaesthetic action of propafenone.

Dose adjustments

Renal

In patients whose liver and/or kidney function is impaired there may be drug accumulation after standard therapeutic doses; such patients can still be titrated on propafenone under ECG and plasma level monitoring.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to propafenone hydrochloride or any excipient
Known Brugada Syndrome
Significant structural heart disease — myocardial infarction within the last 3 months; uncontrolled congestive heart failure with left ventricular output less than 35%; cardiogenic shock (unless arrhythmia-induced)
Severe symptomatic bradycardia; manifest electrolyte imbalance (e.g. potassium metabolism disorders)
Severe obstructive pulmonary disease; severe hypotension
Sinus node dysfunction, atrial conduction defects, second degree or greater AV block, bundle branch block or distal block — unless patients are adequately paced
Co-administration of ritonavir (potential for increased plasma concentrations)
May worsen myasthenia gravis

Side effects

Dizziness (very common)
Cardiac conduction disorders — including sinoatrial, atrioventricular and intraventricular block (very common)
Palpitations (very common); sinus bradycardia, tachycardia, atrial flutter, ventricular tachycardia and other proarrhythmia
Gastrointestinal: nausea, vomiting, abdominal pain, diarrhoea, constipation, dry mouth
Hepatic function abnormal, hepatocellular injury, cholestasis, hepatitis, jaundice
Headache, dysgeusia, vision blurred, hypotension, chest pain, asthenia/fatigue

Interactions

Local anaesthetics (e.g. for pacemaker implantation, surgery or dental work) and other medicines with an inhibitory effect on heart rate and/or myocardial contractility (e.g. beta blockers, tricyclic antidepressants) — potential increase in adverse reactions
Lidocaine — concomitant use reported to increase the risk of CNS side effects of lidocaine
Propranolol, metoprolol, desipramine, ciclosporin, theophylline and digoxin — increased plasma/blood levels reported during propafenone therapy; reduce doses of these as appropriate if signs of overdose are observed
SSRIs (e.g. fluoxetine, paroxetine) — elevated plasma propafenone levels; fluoxetine increased S-propafenone Cmax/AUC by 39% and 50% and R-propafenone Cmax/AUC by 71% and 50% in extensive metabolisers; lower propafenone doses may be required
Ritonavir — contraindicated (see contraindications)

Clinical monograph

How it works

It blocks fast cardiac sodium channels, slowing conduction and prolonging the refractory period, with additional mild beta-adrenoceptor blockade.

Prescribing in practice

Avoid in significant structural heart disease, including ischaemic heart disease and heart failure, because of the proarrhythmic risk seen with class Ic agents.
Use with caution in obstructive airways disease owing to its beta-blocking activity.
It can increase plasma concentrations of digoxin and warfarin, so monitor and adjust accordingly.

Monitoring

Monitor ECG (including QRS duration) and clinical response, particularly when initiating or up-titrating.

Counselling the patient

Report palpitations, fainting, breathlessness or worsening symptoms.
Do not stop or change the dose without medical advice.
Mention any new medicines, as some interact with this drug.

Evidence & guidelines

Class Ic antiarrhythmics are restricted to patients without significant structural heart disease, reflecting the proarrhythmic signal from the CAST trial.

Reference: NICE NG196; ESC; 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.

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