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犬２０只，１２～１８ｋｇ，静脉注射戊巴比妥钠麻醉，监测心电图、希氏束电图、动脉压力及一系列电生理指标，并用ＨＰＬＣ监测美西律的血药浓度变化。窦房结直接给美西律剂量大于１０μｇ时，心率明显降低，与对照组比较１ｍｉｎ心率变化百分率与浓度成负相关。美西律剂量加大到５００μｇ时，心房激动被抑制，心房激动抑制率也有剂量依赖性。静脉注射美西律５ｍｇ·ｋｇ￣（－１）＋３０μｇ·ｋｇ￣（－１）·ｍｉｎ￣（－１），血药浓度维持在２．０μｇ·ｍｌ￣（－１）水平，此时窦房结恢复时间校正值明显延长，其它心脏电生理参数变化无一致性。本实验结果提示大剂量美西律有抑制窦房结的作用。
20 dogs, 12 ~ 18kg, intravenous injection of sodium pentobarbital anesthesia, electrocardiogram, His bundle, arterial pressure and a series of electrophysiological indicators were monitored, and the change of plasma concentration of mexiletine was monitored by HPLC. Sinus node directly to the United States at a dose of more than 10μg, the heart rate was significantly lower than the control group 1min percentage change in heart rate and concentration of a negative correlation. When the dose of mexiletine increased to 500μg, the atrial activation was inhibited and the inhibition rate of atrial activation was also dose-dependent. Intravenous injection of mexiletine 5mg · kg ~ (-1) + 30μg · kg ~ (-1) · min ~ (-1), plasma concentration remained at 2.0μg · ml ~ (-1) level, The correction value of junction recovery time was significantly prolonged, and the changes of other cardiac electrophysiological parameters were not consistent. The experimental results suggest that high-dose mexiletine can inhibit the sinus node.