Lidocaine Dosing and Injection Depth
For local infiltrative anesthesia, inject lidocaine slowly into the deep dermal-subcutaneous tissue plane (not superficially) while withdrawing the needle, using no more than 4.5 mg/kg without epinephrine or 7.0 mg/kg with epinephrine in adults.
Dosing Guidelines
Adults
- Without epinephrine: Maximum 4.5 mg/kg, not exceeding 300 mg total 1, 2
- With epinephrine: Maximum 7.0 mg/kg, not exceeding 500 mg total 1, 2
- For multistage procedures (e.g., Mohs surgery): Up to 500 mg (50 mL of 1% solution) over several hours 1
Children
- Without epinephrine: Maximum 1.5-2.0 mg/kg 1, 2
- With epinephrine: Maximum 3.0-4.5 mg/kg 1, 2
- Reduce doses further in elderly, debilitated patients, or those with cardiac/liver disease 2
Injection Depth Technique
Deep injection is critical for minimizing pain and optimizing safety. Research demonstrates that superficial wheal-producing dermal injection is uniformly much more painful than injection into the deep dermal-subcutaneous tissue region 3.
Optimal Technique:
- Use a 30-gauge needle
- Inject into the deep dermal-subcutaneous tissue plane (not superficially)
- Inject slowly while withdrawing the needle 3
- Inject the smallest volume necessary
- Full anesthesia occurs immediately with superficial injection but takes 5-6 minutes with deep injection 3
The deep injection approach balances pain reduction with adequate anesthesia onset time.
Critical Safety Measures
To prevent local anesthetic systemic toxicity (LAST), which carries significant morbidity risk 1:
- Always use the lowest effective dose
- Aspirate before each injection to avoid intravascular administration
- Use incremental injections rather than bolus dosing
- Continuously monitor the patient for early toxicity signs:
- Circumoral numbness
- Facial tingling
- Metallic taste
- Slurred speech
- Auditory changes
- Progression to seizures or cardiac arrest in severe cases 1
Practical Dosing Calculations
For common concentrations:
- 1% lidocaine = 10 mg/mL
- 2% lidocaine = 20 mg/mL
Example for a 70 kg adult:
- Without epinephrine: Maximum 315 mg (31.5 mL of 1% or 15.75 mL of 2%)
- With epinephrine: Maximum 490 mg (49 mL of 1% or 24.5 mL of 2%)
Special Considerations
Epinephrine significantly delays lidocaine absorption, extending time to peak plasma concentration by over 7 hours, which enhances safety margins 4. This delayed absorption may allow development of systemic tolerance to higher lidocaine levels.
For patients with true lidocaine allergy (rare, <1% of reactions), alternatives include ester-type anesthetics, 1% diphenhydramine, or bacteriostatic normal saline 1.