title: The comparative neurotoxicity of intrathecal lidocaine and bupivacaine in rats.
abstract: There is a considerable difference in the number of reports of neurologic injury in the literature between lidocaine and other local anesthetics. Few in vivo animal studies have produced convincing results showing a difference in neurotoxicity among anesthetics. We investigated whether lidocaine and bupivacaine differ with respect to sensory impairment and histologic damage when equipotent doses of the two are administered intrathecally in rats. First, to determine relative anesthetic potency, rats intrathecally received 20 muL of saline, 0.625%, 1.25%, 2.5%, or 5% lidocaine, or 0.125%, 0.25%, 0.5%, or 1.0% bupivacaine, and were examined with the tail-flick test for 90 min. The potency ratio calculated was approximately 1:4.70 (95% confidence interval, 3.65-6.07) for lidocaine/bupivacaine. In the next experiment, 45 rats intrathecally received 20 muL of saline, 2.13% bupivacaine (approximately 1.5 mg/kg), or 10% lidocaine (approximately 6.9 mg/kg), and were examined for persistent functional impairment and morphologic damage. Rats given lidocaine developed significantly more prolonged tail-flick latencies than those in other groups 4 days after injection and incurred more morphologic damage than those given saline or bupivacaine. In conclusion, although the doses of anesthetics administered were larger than those used clinically, the present results suggest that bupivacaine is less neurotoxic than lidocaine when administered intrathecally at equipotent concentrations in the rat model.
  
  
  CONCLUSIONS
  Bupivacaine induces less severe functional impairment and morphologic damage than lidocaine when the two anesthetics are intrathecally administered at equipotent concentrations in the rat.
authors.affiliation: Departments of *Anesthesiology and †Experimental Animals, Shimane University School of Medicine, Izumo City, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sakura
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kirihara
authors.forename: Tomoko
authors.initials: T
authors.lastname: Muguruma
authors.forename: Tomomune
authors.initials: T
authors.lastname: Kishimoto
authors.forename: Yoji
authors.initials: Y
authors.lastname: Saito
mesh_terms: D000779:Anesthetics, Local / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D002045:Bupivacaine / Q000737:chemistry / Q000633:toxicity*; D002626:Chemistry, Pharmaceutical; D004305:Dose-Response Relationship, Drug; D006614:Hindlimb; D006358:Hot Temperature; D007278:Injections, Spinal; D008012:Lidocaine / Q000737:chemistry / Q000633:toxicity*; D008297:Male; D008854:Microscopy, Electron; D009068:Movement / Q000187:drug effects; D009410:Nerve Degeneration / Q000139:chemically induced / Q000473:pathology; D020258:Neurotoxicity Syndromes; D010147:Pain Measurement / Q000187:drug effects; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000473:pathology
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine; D002045:Bupivacaine