The dose-dependent study of verapamil and diltiazem on spinal anesthesia in the rat

The aim of this study evaluated the spinal anesthetic effect of verapamil and diltiazem. After rats were injected intrathecally with verapamil and diltiazem, dose-response curves were constructed. We evaluated the potency and duration of verapamil or diltiazem which compared with mepivacaine, a commonly used local anesthetic, in rats. Verapamil, diltiazem and mepivacaine produced a dose-dependent local anesthetic effect as spinal anesthesia. On a 50% effective dose (ED50) basis, the spinal anesthetic effect of verapamil was more potent than diltiazem or mepivacaine (P < 0.01 for each comparison). On an equipotent basis (ED25, ED50, and ED75), the blockade duration of spinal anesthesia caused by diltiazem was longer than that caused by verapamil or mepivacaine (P < 0.01 for each comparison). In summary, verapamil produced more potent spinal blockades, when compared with diltiazem or mepivacaine. Diltiazem demonstrated longer spinal blockades than did verapamil or mepivacaine.