Flecainide and Proarrhythmia: is the FAERS signal real?
Flecainide ↔ Proarrhythmia
Flecainide, a sodium-channel-blocking anti-arrhythmic, can paradoxically provoke serious ventricular arrhythmias — a proarrhythmic effect most dangerous in patients with structural heart disease, as tragically shown in the CAST trial, which found increased deaths when these drugs were used after a heart attack. It is a genuine, mechanism-based hazard and is why flecainide is avoided in structural heart disease and started under monitoring. The 99 co-reports (PRR 8.3) reflect both the real effect and the drug's continued use in selected arrhythmias.
Regulatory basis: flecainide prescribing information (proarrhythmia warning; contraindication in structural heart disease). Cardiac Arrhythmia Suppression Trial (CAST).
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Arrhythmias occur during treatment, particularly in structurally abnormal hearts |
| Strength | partial | PRR 8 on a small co-report count |
| Consistency | met | Established by the randomized CAST trial and subsequent studies |
| Specificity | met | A class effect of sodium-channel-blocking anti-arrhythmics |
| Biological gradient | met | Worse in structural heart disease and at higher doses |
| Plausibility | met | Slowed conduction creating re-entry circuits is the mechanism |
| Coherence | met | Coheres with the labelled contraindication in structural heart disease |
| Experiment | met | Randomized evidence (CAST) showed increased mortality |
| Analogy | met | Analogous to proarrhythmia from other class I anti-arrhythmics |
This page's own qualitative read, not an automated/citation-gated assessment.