Local Anesthetics Inhibit Uterine Activity in vitro

Abstract

Objective: Analysis of the effects of local anesthetics upon the gravid uterus. Methods: Isolated strips of pregnant-rat myometrium were placed within tissue baths. Muscular activity was then recorded by a force transducer, at cumulative concentrations of either procaine, lidocaine, or ropivacaine. Results: The effects of myometrial activity were non-monotonic. At lower concentrations, an increase in contraction frequency was noted, concomitant with a depression in amplitude. As the concentrations increased, both amplitude and frequency were depressed until, eventually, activity was abolished. Conclusions: Local anesthetics administered in situ consistently inhibit or completely arrest overall myometrial activity. These agents may prove clinically useful in preterm labor management, if administered locally to the myometrium via suitable slow release drug delivery systems, warranting further trials in vivo.