Antiarrhythmics (adenosine, flecainide, lidocaine)
also: adenosine · flecainide · lidocaine · Vaughan-Williams · SVT
Overview
The antiarrhythmics not covered by the rate-control cards — adenosine for SVT, flecainide for paroxysmal AF, lidocaine for VT — organised by the Vaughan-Williams classification.
Mechanism
Vaughan-Williams: I = Na-channel blockers (Ia procainamide, Ib lidocaine, Ic flecainide); II = β-blockers; III = K-channel blockers (amiodarone, sotalol); IV = non-DHP CCBs. Adenosine is unclassified — transiently blocks the AV node (A1 receptor → ↑K⁺ efflux, hyperpolarisation) → breaks AV-nodal re-entry SVT.
Indications
- SVT (adenosine — diagnostic + therapeutic)
- Paroxysmal AF / "pill-in-the-pocket" (flecainide)
- Ventricular tachycardia (lidocaine/amiodarone)
The agents
rapid IV bolus 6→12→18 mg
Transient flushing/chest tightness/"sense of doom"; very short t½. CI in ASTHMA → use verapamil. Give via a large vein, fast, with a flush.
oral / "pill-in-pocket"
Paroxysmal AF in structurally normal hearts; AVOID post-MI / structural/ischaemic heart disease (pro-arrhythmic).
IV
Ventricular arrhythmias; also a local anaesthetic.
IV
VT, and AF in WPW pre-excitation.
Adverse effects
Brief — but contraindicated in asthma.
Increased mortality post-MI (CAST trial) — structural heart disease is the contraindication.
Cautions & contraindications
Bronchospasm — use verapamil for SVT instead.
Pro-arrhythmic, ↑mortality.
Promote accessory-pathway conduction → VF.
Interactions
- Dipyridamole potentiates adenosine; theophylline blocks it
- Flecainide + AV-node blockers
Monitoring & kinetics
Continuous ECG during adenosine/IV antiarrhythmics
Adenosine IV push (seconds); flecainide oral; lidocaine/procainamide IV.
Source: Resus Council UK — Tachycardia · BNF — Antiarrhythmics