Duration of Lidocaine with Epinephrine for Foot Injection
Lidocaine with epinephrine for foot injection typically lasts between 90-200 minutes, with the addition of epinephrine significantly prolonging the duration compared to plain lidocaine.
Mechanism of Action and Duration
Lidocaine with epinephrine provides longer-lasting anesthesia due to the vasoconstrictive properties of epinephrine, which:
- Decreases local blood flow at the injection site
- Slows the clearance of lidocaine from the tissue
- Increases the amount of lidocaine in the slow-decaying component within the nerve by 3-4 fold 1
Duration Specifics
According to established guidelines, the duration of action for lidocaine with epinephrine when used for nerve block or infiltration is:
- 90-200 minutes for lidocaine with epinephrine 2
- This is approximately twice as long as plain lidocaine, which typically lasts 45-90 minutes
Dosing Considerations
When administering lidocaine with epinephrine for foot injections, several important dosing parameters should be observed:
- Maximum safe dose: 7 mg/kg with epinephrine (compared to 4.4 mg/kg without epinephrine) 2
- Concentration of epinephrine: Even very dilute concentrations (as low as 1:3,200,000) can still increase duration of anesthesia by approximately 100% 3
- Standard concentrations of 1:200,000 or 1:50,000 can increase duration by approximately 200% 3
Clinical Application for Foot Injections
For foot injections specifically:
- The subcutaneous injection of lidocaine around the ankle can provide effective analgesia lasting up to 11 hours (median) in patients with critical limb ischemia 4
- The prolonged duration makes lidocaine with epinephrine particularly useful for procedures requiring extended anesthesia
Safety Considerations
When using lidocaine with epinephrine, important safety considerations include:
- Avoid concurrent use with other local anesthetics within their period of action
- Do not start intravenous lidocaine within 4 hours of any nerve block or fascial plane block 2
- Be vigilant for early signs of lidocaine toxicity, which include peri-oral tingling, tinnitus, light-headedness, and restlessness 2
- Have lipid emulsion 20% readily available for treatment of potential toxicity 2
Optimizing Anesthetic Effect
To maximize the effectiveness and comfort of lidocaine with epinephrine injections:
- Consider buffering the solution with sodium bicarbonate (1:9 or 1:10 ratio) to decrease injection pain 2
- Use slow infiltration rate to minimize discomfort during administration
- Warm the solution to approximately 40°C to reduce pain during injection 2
Lidocaine with epinephrine remains the preferred choice for foot injections requiring extended duration of action, providing approximately twice the duration of anesthesia compared to plain lidocaine while maintaining a favorable safety profile when used appropriately.