A Comparison of Buffered and Non-Buffered 2% Lidocaine with Epinephrine, a Pilot Study

A Comparison of Buffered and Non-buffered 2% Lidocaine with Epinephrine, A Pilot Study

Lidocaine with vasoconstrictors are acidic, pH 3.5, to extend shelf-life and are buffered by the patient’s tissue fluids to a neutral pH once injected. Only the non-ionized drug form crosses the nerve membrane to effect anesthesia. At pH 7.4 less than half of the drug dosage is the unionized form, pKa 8. Buffering lidocaine with bicarbonate just prior to injection maximizes the active drug available to the nerve trunk resulting in faster onset and, deeper anesthetic effect. With a neutral pH pain also is reduced on injection (1,2). However, a limited number of clinical studies address the topic.

This prospective, randomized, double-blind, crossover trial (N=23) assessed the clinical impact of buffered lidocaine with 1/100k Epi (Anutra Medical, RTP, NC) as compared to the non buffered drug. After an inferior alveolar nerve block, 80mg of either buffered or unbuffered drug, subjects reported pain on injection using a 10-pt-likert type scale and time to lower lip numbness. Prior to nerve block, a few drops of the same drug was dropped on the exposed dry surface of the contralateral lip to assess for topical effect, yes or no. Subjects at two weeks were tested with the alternate drug combinations and the same outcomes were reported.

Predictor variables were the alternate drug formulations. Outcome variables were subjects’ subjective responses to topical lip numbness, pain on injection, and time to lower lip numbness. Data from encounter forms for subjects’ subjective responses were entered (Teleform) into an ACCESS database. Descriptive statistics were analyzed with SAS (Cary, NC) software.

Females were 48% of subjects. Half were Caucasian, 22% African America, and 13% Asian. Median age was 21 y.(IQR 20, 22y). Median body weight was 147lbs.(IQR 130, 170lbs.). When subjects were administered the buffered drug, time to lower lip numbness was less for 13 subjects(57%), the same for 2 subjects(8%), and greater for 8 subjects(35%). Eighteen subjects(78%) reported lower or the same pain scores as compared to the non-buffered drugs. A positive topical effect of both drugs combinations were reported for 20 subjects(87%).

Based on the data we report nerve block with buffered lidocaine with Epi produces less pain on injection and reduces the onset of anesthesia as compared to the non-buffered drug combination. Additional studies with field block in the maxilla with the same drug combinations and a comparison of buffered 2% vs. non-buffered 4% articaine should be conducted.

Buffering local anesthetic drugs with Epi can produce outcomes favorable for patients and clinicians.

1) Giovannitti, Joseph A., Morton B. Rosenberg, and James C. Phero. "Pharmacology of Local Anesthetics Used in Oral Surgery." Oral and Maxillofacial Surgery Clinics of North America25.3 (2013): 453-65. Web.

2) Malamend, Stanley F. "Buffering Local Anesthetics in Dentistry." The Pulse 44.1 (2011): 7-9.