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Class IC Antiarrhythmic

Flecainide

Brand names: Tambocor

Used in: Atrial Fibrillation

Flecainide is a class Ic antiarrhythmic used for paroxysmal atrial fibrillation and some supraventricular tachycardias in patients with structurally normal hearts (including as a 'pill-in-the-pocket').

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION For patients with sustained VT, no matter what their cardiac status, flecainide acetate tablets, like other antiarrhythmics, should be initiated in-hospital with rhythm monitoring. Flecainide has a long half-life (12 to 27 hours in patients). Steady-state plasma levels, in patients with normal renal and hepatic function, may not be achieved until the patient has received 3 to 5 days of therapy at a given dose. Therefore, increases in dosage should be made no more frequently than once every four days, since during the first 2 to 3 days of therapy the optimal effect of a given dose may not be achieved. For patients with PSVT and patients with PAF the recommended …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-01-09. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It blocks cardiac sodium channels, slowing conduction; this is antiarrhythmic in normal hearts but proarrhythmic where there is scar or ischaemia.

Prescribing in practice

  • Avoid in ischaemic or structural heart disease and in significant left-ventricular dysfunction — it increased mortality in such patients (CAST trial).
  • It is proarrhythmic; in atrial flutter/AF it is usually combined with an AV-nodal blocker to avoid 1:1 conduction.
  • Reduce the dose in renal or hepatic impairment; levels can be measured where toxicity is suspected.

Monitoring

Confirm a structurally normal heart before use; monitor ECG (QRS widening) and, where relevant, plasma levels.

Counselling the patient

  • Report palpitations, dizziness or blackouts.
  • Take it exactly as prescribed; for 'pill-in-the-pocket' use, follow the specific instructions you were given.

Evidence & guidelines

Effective for paroxysmal AF/SVT in structurally normal hearts, but contraindicated in structural/ischaemic heart disease (CAST).

Reference: CAST Trial (NEJM 1989); ESC AF Guidelines 2020; ESC SVT Guidelines 2019; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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