This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (34) Citing Articles via Google Scholar Google Scholar Articles by Lacassie, H. J. Articles by Columb, M. O. Search for Related Content PubMed PubMed Citation Articles by Lacassie, H. J. Articles by Columb, M. O. Related Collections Obstetrics Regional Anesthesia

---

OBSTETRIC ANESTHESIA

The Relative Motor Blocking Potencies of Bupivacaine and Levobupivacaine in Labor

Héctor J. Lacassie, MD^*, and Malachy O. Columb, FRCA

*Anesthesiology Department, Pontificia Universidad Católica de Chile, Santiago, Chile; and South Manchester University Hospital, Wythenshawe, United Kingdom

Address correspondence to Héctor J. Lacassie, MD, Department of Anesthesiology, Pontificia Universidad Católica de Chile, Marcoleta 367, 3rd Fl., Santiago, Chile. Address e-mail to lacassie{at}med.puc.cl Reprints will not be available from the author.

Minimum local analgesic concentrations (MLAC) have been used to determine the epidural analgesic potencies of bupivacaine and its levo- counterpart. There are no reports of the motor blocking potencies of these drugs. In this study we sought to determine the motor block MLAC of both drugs and determine the relative potency ratio. Sixty ASA physical status I–II parturients were randomized. The first woman in each group received 0.25% wt/vol. Up-down sequential allocation was used to determine subsequent concentrations at a testing interval of 0.025% wt/vol. Effective motor block was defined as a Bromage score <4 within 30 min. The up-down sequences were analyzed with the Dixon and Massey method and probit regression. Two-sided P < 0.05 defined significance. The motor block MLAC for bupivacaine was 0.27% wt/vol (95% confidence interval [CI], 0.25–0.30) and for levobupivacaine was 0.31% wt/vol (95% CI, 0.29–0.34) (P = 0.024), with a levobupivacaine/bupivacaine potency ratio of 0.87 (95% CI, 0.77–0.98). This is the first study to estimate the motor-blocking potency ratio of bupivacaine and levobupivacaine in labor. This study demonstrates that the S-enantiomer of bupivacaine is less potent at motor block than the racemate.

IMPLICATIONS: We estimated the motor-blocking potency ratio of bupivacaine and levobupivacaine in labor and demonstrated that the S-enantiomer of bupivacaine is less potent at motor block than the racemate.

This article has been cited by other articles:

				P. Ingelmo, G. Frawley, M. Astuto, C. Duffy, S. Donath, N. Disma, G. Rosano, R. Fumagalli, and A. Gullo Relative Analgesic Potencies of Levobupivacaine and Ropivacaine for Caudal Anesthesia in Children Anesth. Analg., March 1, 2009; 108(3): 805 - 813. [Abstract] [Full Text] [PDF]

				A. Tyagi, A. Kumar, A. K. Sethi, and M. Mohta Epidural Volume Extension and Intrathecal Dose Requirement: Plain Versus Hyperbaric Bupivacaine Anesth. Analg., July 1, 2008; 107(1): 333 - 338. [Abstract] [Full Text] [PDF]

				Y. Beilin, N. R. Guinn, H. H. Bernstein, J. Zahn, S. Hossain, and C. A. Bodian Local Anesthetics and Mode of Delivery: Bupivacaine Versus Ropivacaine Versus Levobupivacaine Anesth. Analg., September 1, 2007; 105(3): 756 - 763. [Abstract] [Full Text] [PDF]

				H. J. Lacassie, H. P. Lacassie, and M. O. Columb Reflections on Motor Blocking Minimum Local Anesthetic Concentrations Anesth. Analg., June 1, 2007; 104(6): 1609 - 1609. [Full Text] [PDF]

				M. Camorcia, G. Capogna, C. Berritta, and M. O. Columb The Relative Potencies for Motor Block After Intrathecal Ropivacaine, Levobupivacaine, and Bupivacaine Anesth. Analg., April 1, 2007; 104(4): 904 - 907. [Abstract] [Full Text] [PDF]

				R. W.-L. Goy, Y. Chee-Seng, A. T.-H. Sia, K. Choo-Kok, and S. Liang The Median Effective Dose of Intrathecal Hyperbaric Bupivacaine Is Larger in the Single-Shot Spinal as Compared with the Combined Spinal-Epidural Technique Anesth. Analg., May 1, 2005; 100(5): 1499 - 1502. [Abstract] [Full Text] [PDF]