目的 观察乌头注射液镇痛作用的强弱及其药效动力学过程，求出相应的药效动力学参数，为合理用药作参考。方法 用热板法测定小鼠疼痛反应的潜伏期为痛阈指标，以吗啡为阳性对照药，进行药物镇痛作用的研究，以一次给药后药效强度变化的经时过程进行房室模型拟合和药效动力学参数计算。结果 显示乌头注射液具有显著的镇痛作用，其2 mg·kg^-1 ip作用强度与吗啡10 mg·kg^-1 ip相当。药效消除基本呈一级动力学过程并基本符合血管外给药的一房室开放模型，其吸收相速率常数K为0.02654 min^-1，药效倍增期为26.12 min，其消除相速率常数K为0.007968 min^-1，药效半衰期t_1/2E为87 min，其药效达峰时间为80.16 min，峰强度为149.24 ΔE%(58.27 s)。药效持续时间约为6～7 h。结论 乌头注射液具有肯定的镇痛作用，其药效强度较高，维持时间较长。其药效动力学参数，可为临床用药作参考。

OBJECTIVE To study the analgesia effects and pharmacodynamics of Wutou injection.METHODS The mice were treated ip once with Wutou injection (2 mg·kg^-1) and morphine (10 mg·kg^-1) was used as the positive control.The changes of reactive latent period on hot-plate were observed.The apparent parameters of pharmacodynamics were estimated based on the time-effect curve.RESULTS The Wutou injection had analgesic effect obviously.Its effect-time curve ws conformed to one-compartment modle of extravascular administration.The apparent parameters of the pharmacodynamics were:Ka=0.026539 min^-1;t_1/2a=26.12 min;k_e=0.007968 min^-1;t_1/2E=87 min;t_max=80.16 min;E_max=149.24 ΔE%(58.27 s),respectively.CONCLUSION The Wutou injection had analgesic effect obviouly.The parameters of pharmacodynamics may be helpful for physicians clinic.