Diluting 2% Lidocaine with Normal Saline to Achieve 1% Concentration
Yes, it is acceptable to dilute 2% plain lidocaine with an equal volume of normal saline to obtain a 1% lidocaine solution, as explicitly permitted by FDA labeling. 1
FDA-Approved Practice
The FDA drug label for lidocaine explicitly states: "In some cases it will be necessary to dilute available concentrations with 0.9% sodium chloride injection in order to obtain the required final concentration." 1 This directly addresses your question and confirms that diluting 2% lidocaine with normal saline is an approved practice.
Important Caveats About Efficacy
While dilution is permitted, you should be aware that diluted lidocaine may be less potent than commercially prepared solutions at the same concentration:
For epidural use specifically: Research demonstrates that 2% lidocaine diluted 1:1 with saline produces significantly less potent epidural blockade than commercially prepared 1% lidocaine 2, 3
- Narrower sensory spread
- Shorter duration of action
- Reduced motor blockade
For infiltrative/subcutaneous use: The evidence is more favorable. Studies show diluted lidocaine can actually reduce injection pain while maintaining adequate anesthesia 4, 5, 6
Practical Recommendations
For office-based dermatologic procedures (biopsies, excisions, minor surgeries):
- Diluting 2% lidocaine with normal saline is appropriate and may improve patient comfort during injection 7
- The 2016 AAD guidelines recommend using "the lowest effective concentration" 7
- Recent evidence suggests even greater dilutions (up to 1:6) maintain efficacy while reducing injection pain and total lidocaine dose 6
For epidural/regional anesthesia:
- Consider using commercially prepared 1% lidocaine instead of diluting 2% solution if available
- If dilution is necessary, anticipate potentially reduced block quality and adjust your technique accordingly
Safety Considerations
When diluting lidocaine, always remember:
- Calculate total milligrams of lidocaine, not just volume or concentration 7
- Maximum safe doses remain: 4.5 mg/kg without epinephrine, 7.0 mg/kg with epinephrine in adults 7, 1
- Dilution does not change the total drug dose—only the concentration and volume
- Use preservative-free normal saline for epidural/spinal applications
The mathematical conversion is straightforward: mixing 10 mL of 2% lidocaine (200 mg) with 10 mL normal saline yields 20 mL of 1% lidocaine (still 200 mg total).