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Plasma Concentrations of Lidocaine and Its Principal Metabolites During Continuous Epidural Infusion of Lidocaine With or Without Epinephrine
  1. Shin-ichi Kihara, M.D.,
  2. Masayuki Miyabe, M.D.,
  3. Yoshihiro Kakiuchi, B.S.P.,
  4. Shinji Takahashi, M.D.,
  5. Taeko Fukuda, M.D.,
  6. Yukinao Kohda, Ph.D. and
  7. Hidenori Toyooka, M.D.
  1. From the Departments of Anesthesiology and Clinical Pharmacy. Institute of Clinical Medicine, University of Tsukuba. Tsukuba, Japan.
  1. Reprint requests: Masayuki Miyabe, M.D., Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba 305-8575, Japan.


Background and Objectives. The purpose of this study was to evaluate the effect of epinephrine on the absorption of lidocaine and the accumulation of active metabolites of lidocaine during continuous epidural anesthesia.

Methods. Lidocaine was administered as an initial bolus of 5 mg/kg of 2% lidocaine solution followed by continuous infusion at 2.5 mg/kg/h. Patients in group I (n = 10) received lidocaine alone and patients in group II (n = 10) received lidocaine + epinephrine (5 μg/mL). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15 minutes, 30 minutes, and 1, 2, and 3 hours of infusion using high-performance liquid chromatography with ultraviolet detection.

Results. Plasma lidocaine concentrations were higher in group I for the first 30 minutes; however, after 1 hour the levels were the same. Plasma MEGX and GX increased continuously in both groups. MEGX levels the were significantly higher in group I, but there was no significant difference in the sum of lidocaine + MEGX after 2 hours. There was no significant difference in GX levels between the two groups.

Conclusions. With respect to continuous epidural administration, addition of epinephrine to lidocaine solutions is ineffective after 2 hours for reducing the potential for systemic toxicity, because the sum of the plasma concentrations of lidocaine and its principal active metabolite, MEGX, are unaffected.

  • epidural anesthesia
  • lidocaine
  • epinephrine.

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