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Use of a Charged Lidocaine Derivative, Tonicaine, for Prolonged Infiltration Anesthesia
  1. Mohammed A. Khan, M.D.,
  2. Peter Gerner, M.D.,
  3. Yukari Sudoh, M.D. and
  4. Ging Kuo Wang, Ph.D.
  1. From the Department of Anesthesiology, Tufts University School of Medicine and New England Medical Center (M.A.K.) and the Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital and Harvard Medical School (P.G., Y.S., G.K.W.), Boston, Massachusetts.
  1. Reprint requests: Peter Gerner, M.D., Department of Anesthesiology and Pain Medicine, Brigham & Women’s Hospital, 75 Francis St, Boston, MA 02115. E-mail:


Background and Objectives We tested the hypothesis that the duration of cutaneous anesthesia elicited by the permanently charged compound N-phenylethyl lidocaine (tonicaine) would be longer than that elicited by its parent structure, lidocaine, and that it would be less affected by epinephrine (epi), after subcutaneous injection in rats, as a model for infiltration anesthesia.

Methods Subcutaneous injections were performed on the shaved dorsal skin of rats with either tonicaine or lidocaine (0.1% or 0.5%, n = 8 in each group) with and without epi (1:200,000). Inhibition of the cutaneous trunci muscle reflex was quantitatively evaluated by a blinded observer by the number of times pinpricks failed to elicit the nocifensive motor response out of a total of 6 pinpricks applied to the injected area.

Results Duration of complete nociceptive blockade in the 0.5% tonicaine and lidocaine groups was 619 ± 47 and 58 ± 2 minutes, respectively; duration of full recovery in these groups was 1,106 ± 19 and 86 ± 3 minutes, respectively. Epi increased the duration of complete block in the 0.5% tonicaine and lidocaine groups to 750 ± 13 and 97 ± 11 minutes, respectively, and the duration of full recovery to 1,185 ± 13 and 172 ± 6 minutes, respectively. Skin toxicity was seen only in the 0.5% tonicaine with epi group (3 of 8 rats).

Conclusions Tonicaine is a substantially longer lasting local anesthetic with a delayed onset of action compared with lidocaine and may be useful in situations where long duration of infiltration block is desirable.

  • Infiltration anesthesia
  • Pain management
  • Sodium channel blocker
  • Postoperative pain

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  • Supported by Grants No. GM48090 (to G.K.W.) and GM07592 (to P.G.) from the National Institutes of Health, Bethesda, MD.

    This study was conducted at the Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA.