New amide local anesthetics for obstetric use

The introduction of stereo-specific levorotary isomers of amide local anesthetics, ropivacaine and levobupivacaine, for clinical use is important. This is because these drugs have a wider margin of safety, but similar blocking properties to the currently available formulation of racemic bupivacaine, although at a higher cost. However, it is noteworthy that modifications in clinical practice, such as the use of appropriate test doses and fractionation of the induction dose, have made epidural use in obstetrics a very safe procedure even before the introduction of these new drugs. Thus, because of their greater cost, it is difficult to predict what role, if any, these amides will assume in obstetric practice without a cost-benefit analysis. From the standpoint of systemic toxicity, the anticipated benefit of these drugs during routine epidural analgesia for labor is questionable because of the widespread use of very dilute concentrations of local anesthetic by continuous infusion. Their use, in theory, may be more beneficial to women having a cesarean section where relatively higher volumes and concentrations of local anesthetics are required for satisfactory sensory and motor block. Nonetheless, in no circumstance should a greater margin of safety be relied on as a substitute for proper technique.