Procaine, lidocaine, and ketamine inhibit histamine-induced contracture of guinea pig tracheal muscle in vitro.

In vitro experiments using guinea pig tracheal smooth muscle were performed to compare the relaxant properties of procaine, lidocaine, and ketamine following contracture induced by histamine. Procaine produced a spasmolytic effect in a dose-related manner. In the doses tested, relaxation induced by procaine was more pronounced than that produced by either lidocaine or ketamine, although the latter 2 drugs also had a significant spasmolytic effect.