Duration of Action of IV Lidocaine Induction Dose
An induction dose of intravenous lidocaine (1.5 mg/kg given over 10 minutes) has a duration of action of approximately 1.5 to 2 hours based on its elimination half-life, though therapeutic effects may begin to wane earlier. 1
Pharmacokinetic Profile
The elimination half-life of lidocaine following IV bolus administration is typically 1.5 to 2.0 hours in patients with normal hepatic function 1. This represents the time required for plasma concentrations to decrease by 50%, which directly determines the duration of clinical effect.
Key Temporal Characteristics:
Onset of action is rapid following IV administration, with peak blood levels occurring as early as 5 minutes after administration 1
The therapeutic window is relatively short for a single bolus dose, as lidocaine is metabolized rapidly by the liver 1
For a standard induction dose of 1.5 mg/kg given over 10 minutes, clinically significant effects typically last 45 minutes to 2 hours based on the drug's pharmacokinetics 2, 1, 3
Clinical Context from Research
A study examining lidocaine's effects on central pain demonstrated that a 5 mg/kg IV dose given over 30 minutes provided significant pain reduction for up to 45 minutes after injection, suggesting that even higher doses have limited duration without continuous infusion 3. This aligns with the elimination half-life data and confirms the relatively brief duration of action.
Important Pharmacokinetic Considerations
Approximately 90% of administered lidocaine is metabolized to various metabolites, with less than 10% excreted unchanged 1
The elimination half-life may be prolonged two-fold or more in patients with liver dysfunction, potentially extending the duration of action but also increasing toxicity risk 1
Renal dysfunction does not affect lidocaine kinetics but may lead to accumulation of metabolites 1
Lidocaine exhibits time-dependent pharmacokinetics after 12 hours of continuous infusion, with the half-life prolonging from approximately 100 minutes to 3.22 hours after 24 hours of infusion 4, 5
Clinical Implications
For procedures requiring longer anesthetic effect, a continuous infusion following the bolus dose is necessary to maintain therapeutic plasma concentrations. The standard approach uses a 1.5 mg/kg loading dose over 10 minutes followed by an infusion rate that does not exceed 120 mg/hour 2.