Pharm 101: Lignocaine

Class

Local anaesthetic
Class IB antiarrhythmic

Pharmacodynamics

• Class IB antiarrhythmic drug that shortens action potential duration
• Blocks activated and inactivated Na channels with rapid kinetics
• Inactivated state block means greater effect on cells with long action potentials such as Purkinje fibres and ventricular cells, compared with atrial cells
• No effect on conduction

Pharmacokinetics

• Can be administered via ETT
• Given IV due to extensive first pass metabolism
• Half-life 1-2 hours

Clinical uses

• Arrhythmias associated with MI
• VT
• Local anaesthetic
• Maximum dose:
  • 4mg/kg plain
  • 7mg/kg with adrenaline

Adverse effects

• Dose-related and short-lived
• Transient neurological symptoms:
  • Paraesthesias
  • Tremor
  • Nausea
  • Tinnitus
• Toxicity:
  • CVS: proarrhythmic effects, hypotension in CCF, cardiovascular collapse
  • CNS: metallic taste in mouth, tongue numbness, sedation, hallucinations, seizures

Precautions/contraindications

• Reduce dose in heart failure or liver disease

Further Reading

• Nickson C. Local Anaesthetic Toxicity
• Nickson C. Anti-arrhythmic drugs and cardiac arrest