title: The relative potencies for motor block after intrathecal ropivacaine, levobupivacaine, and bupivacaine.
abstract: BACKGROUND
  In this study, we sought to determine the median effective dose (ED50) for motor block of intrathecal ropivacaine, levobupivacaine, and bupivacaine and to define their motor-blocking potency ratios.
  
  
  METHODS
  We enrolled 104 parturients undergoing elective cesarean delivery with combined spinal-epidural anesthesia and randomized them to one of three groups to receive intrathecal 0.5% (wt/vol) ropivacaine, levobupivacaine, or bupivacaine. The initial dose was 4 mg, and the testing interval was set at 1 mg. Efficacy was determined by the occurrence of any motor block in either lower limb (modified Bromage and hip motor function scale) within 5 min after the spinal injection.
  
  
  RESULTS
  As assessed using up-down analysis, intrathecal ED50 for motor block was 5.79 mg for ropivacaine (95% CI 4.62-6.96), 4.83 mg for levobupivacaine (95% CI 4.35-5.32) and 3.44 mg for bupivacaine (95% CI 2.55-4.34) (P < 0.0007). The relative motor blocking potency ratios were ropivacaine/bupivacaine 0.59 (95% CI, 0.42-0.82), ropivacaine/levobupivacaine 0.83 (95% CI 0.64-1.09), and levobupivacaine/bupivacaine 0.71 (95% CI 0.51-0.98).
  
  
  CONCLUSIONS
  There is a clinical profile of potency for motor block for the pipecolylxylidines when administered spinally: low, intermediate, and high for ropivacaine, levobupivacaine, and bupivacaine, respectively.
authors: Department of Anesthesia, Città di Roma Hospital, Roma, Italy. michela_camorcia@yahoo.it
authors: Michela
authors: M
authors: Camorcia
authors: Giorgio
authors: G
authors: Capogna
authors: Cristiana
authors: C
authors: Berritta
authors: Malachy O
authors: MO
authors: Columb
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D000767:Anesthesia, Epidural / Q000379:methods; D000773:Anesthesia, Obstetrical / Q000379:methods; D000775:Anesthesia, Spinal / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002045:Bupivacaine / Q000008:administration & dosage* / Q000031:analogs & derivatives; D002585:Cesarean Section; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D007278:Injections, Spinal; D000077554:Levobupivacaine; D009043:Motor Activity / Q000187:drug effects*; D009407:Nerve Block; D011446:Prospective Studies; D000077212:Ropivacaine
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D000077554:Levobupivacaine; D002045:Bupivacaine