From the Guidelines
Toxic Dose of Lidocaine
The toxic dose of lidocaine is generally considered to be greater than 500 mg when administered intravenously, with severe toxicity typically occurring at doses exceeding 1000 mg 1.
- For local administration, the maximum recommended dose is 7.0 mg/kg with epinephrine, and 4.4 mg/kg without epinephrine, not to exceed 300 mg for medical use and 4.4 mg/kg for dental use 1.
- The duration of action of lidocaine is 90-200 minutes 1.
- For intravenous administration, a loading dose of no more than 1.5 mg/kg is recommended, given as an infusion over 10 minutes 1.
- It is essential to monitor patients closely during lidocaine administration, with continuous ECG and pulse oximetry, and regular non-invasive blood pressure checks every 5 minutes during the initial infusion and for the first 15 minutes thereafter 1.
- The maximum infusion rate for intravenous lidocaine is 4 mg/min.
- Lower doses should be used in very vascular areas, and in infants younger than 6 months, doses of amides, such as lidocaine, should be decreased by 30% 1.
From the Research
Toxic Dose of Lidocaine
The toxic dose of lidocaine can vary depending on several factors, including the technique of administration, the presence of adrenaline, and individual patient characteristics.
- The half effective doses (ED50) of lidocaine for altered state of consciousness (ASC) was 3.1 mg/kg, for arrhythmia was 3.0 mg/kg, and for death was 23.1 mg/kg 2.
- Preliminary estimates for maximum safe dosages of tumescent lidocaine are 28 mg/kg without liposuction and 45 mg/kg with liposuction 3.
- Recommended maximum doses of lidocaine are 400 mg for subcutaneous injection, 200 mg for injection in regions of high absorption, 400 mg for single injection, 500 mg for protracted injection, and 1-25 ml for injection into vasoactive regions 4.
- A retrospective chart review of 563 patients who received over 30 mL of locally injected lidocaine found that only two complications could be attributable to local anesthetics, and the safety of high volumes of lidocaine extends to patients with risk factors such as heart disease, hypertension, diabetes, and smoking 5.
- A prospective study of six female patients undergoing elective facelift surgery found that a mean lidocaine dose of 21.6 mg/kg infiltrated subcutaneously over 20 minutes or less resulted in a peak plasma lidocaine level that was 72% below the level considered safe (5 microg/mL) 6.
Factors Affecting Toxicity
Several factors can affect the toxicity of lidocaine, including:
- Technique of administration: The technique of administration can affect the rate of absorption and the peak plasma concentration of lidocaine 3, 4.
- Presence of adrenaline: The presence of adrenaline can affect the toxicity of lidocaine, with some studies suggesting that adrenaline can reduce the toxicity of lidocaine 2, 4.
- Individual patient characteristics: Individual patient characteristics, such as weight and medical history, can affect the toxicity of lidocaine 4, 5.