Virtually Painless Local Anesthesia: Diluted Lidocaine Proves to Be Superior to Buffered Lidocaine for Subcutaneous Infiltration

October 2012 | Volume 11 | Issue 10 | Original Article | 39 | Copyright © October 2012


Background: Many physicians believe that buffering local anesthetics with sodium bicarbonate is the best technique for reducing the pain and discomfort associated with subcutaneous infiltration.
Objective: To compare the level of pain and discomfort associated with subcutaneous infiltration of lidocaine diluted with normal saline to that associated with traditionally buffered lidocaine.
Patients/Methods: In a prospective, double-blind trial, 31 patients were asked to use a visual analog scale to rank the level of pain and discomfort caused by two different solutions of lidocaine with epinephrine. Solution A: 3 mL of 1% lidocaine + epinephrine in 30 mL of bacteriostatic 0.9% sodium chloride in a 1:10 ratio, in which each mL contained 9 mg of sodium chloride and 9 mg of benzyl alcohol. Solution B: 5 mL of 8.4% sodium bicarbonate solution and 50 mL of 1% lidocaine + epinephrine in a 1:10 ratio.
Results: Twenty-eight out of 31 patients reported that the solution of lidocaine diluted with normal saline was the least painful upon injection.
Conclusion: Pain and discomfort during subcutaneous injection of lidocaine can be reduced by diluting the anesthetic with normal saline in a 1:10 ratio.

J Drugs Dermatol. 2012;11(10):e39-e42.


Of all the procedures that the average dermatologist performs today, none is more common than the skin biopsy. Although the premise behind local anesthesia is to reduce the pain and discomfort associated with many procedures, it is often the infiltration of the skin with anesthetic that is perceived by the patient as being the most unpleasant part of his or her dermatology visit.
Several experiments have been conducted in order to offer patients a more pleasant experience during the subcutaneous injection of local anesthetics (LAs). Tactile stimulation, cooling devices, and warming and buffering of the LAs, as well as prior application of topical anesthetics, are all techniques that have been used to minimize the pain of injection and infiltration of LAs.
Although buffered lidocaine has been shown to be effective at reducing pain during subcutaneous infiltration,1 patients still report pain and discomfort during this procedure. The aim of this study is to compare the clinical efficacy of pain attenuation using lidocaine with epinephrine diluted with normal saline vs lidocaine with epinephrine buffered with sodium bicarbonate.


The study protocol and all related materials were registered, approved, and monitored by the University of Miami Institutional Review Board. Informed consent was obtained from 31 patients who needed two biopsies of the facial area, seen in a private, community-based hospital clinic over a period of two months. Participant demographics included Caucasian and Hispanic males and females, aged 25 to 85 years old, who needed facial biopsies (ie, either shave or punch) to rule out potential skin cancer. All patients in the study denied any allergy to lidocaine or sensitivity to epinephrine.
The same medical assistant prepared two different fresh solutions of lidocaine with epinephrine for each biopsy:
Solution A (unbuffered): 3 mL of 1% lidocaine and epinephrine in 30 mL of bacteriostatic 0.9% sodium chloride in a 1:10