Buffered local anesthetics and epinephrine degradation

Lidocaine with epinephrine is currently the most common local anesthetic agent used for facial soft tissue surgery. This combination is generally safe and effective in providing complete anesthesia and adequate hemostasis. Because epinephrine is unstable at physiologic pH, the commercial preparation is formulated with a low pH (3.5-5.5). Unfortunately, this acidic pH causes significant pain during infiltration. To reduce pain, clinicians sometimes buffer acidic local anesthetic agents with sodium bicarbonate. However, little is known about the stability of epinephrine when the pH of epinephrine is clinically altered. Using high pressure liquid chromatography (HPLC), epinephrine levels were measured after the addition of sodium bicarbonate. Our results indicate a significant amount of epinephrine degradation occurs in some of these specimens. Recommendations regarding the use of buffered local anesthetic agents are made.