Core pharmacology

Class Group

Antiarrhythmic –
Vaughan Williams Class Ia
Na channel blocker

Legacy Cicm Level

-

Introduction

Aminobenzamides local anaesthetic
Class Ia antiarrhythmic
Na channel blocker

Indications Uses

Local or regional anesthesia
Treatment of VT during cardiac manipulation (surgery, cath), AMI, digitalis toxicity

Presentation

PO
IV: 100mg/mL (10 mL); 500mg/mL (2 mL)

Mechanism of action

Blocks Na channels.
stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses thereby effecting local anesthetic action.

Physiological effects

Ventricular excitability is depressed and the stimulation threshold of the ventricle is increased during diastole. The sinoatrial node is, however, unaffected.

Adverse Effects Toxicity

Myocardial depression
Watch for QRS/QT segment prolongation, ventricular tachycardia, ventricular fibrillation, complete atrioventricular block, torsades de pointes.
Abnormal LFTs
GI intolerance

Absorption

PO/IV.
BA 75-95%

Protein binding

15-20%

Volume of distribution

2 L/kg

Metabolism

Hepatic. 1 main metabolite: N-Acetyl-3-hydroxyprocainamide

Excretion

Urine (30-60% unchanged)

Half-life

2.5-4.5 hrs

Route And Dose

PO / IV.
IV loading: 15-18mg/kg over 30min
Maintenance: 1-4mg/min