Minami M, Togashi H, Yoshioka M
Nihon Yakurigaku Zasshi. 1985 Oct;86(4):241-55. doi: 10.1254/fpj.86.241.
Imidazoline derivatives, clonidine and guanfacine, were reviewed with respect to their effect on blood pressure. Excitation of the central alpha-adrenoceptors induced by clonidine or guanfacine produced a simultaneous decrease in peripheral sympathetic tone, hypotension and bradycardia. Both ponto-medullary regions and the hypothalamus are important action sites for these two drugs. With respect to the effects of clonidine or guanfacine on central alpha-adrenoceptors, two possibilities were investigated. First, we presumed that the excitation of central alpha-adrenoceptors induced by these two drugs appears to be located at postsynaptic sites. Thus, the alpha 2-subtype was considered. Secondarily, stimulation of the central presynaptic alpha 2 receptor produced by clonidine or guanfacine could not be excluded completely. It has been reported that after abrupt cessation of guanfacine, a withdrawal syndrome infrequently occurs which is moderate as compared with that caused by the abrupt cessation of clonidine. In comparison with clonidine, the characteristics of guanfacine pharmacokinetics, including its large volume of distribution, long biological half life and long duration of action, appear to be associated with the infrequent occurrence of withdrawal syndrome after guanfacine cessation.
对咪唑啉衍生物可乐定和胍法辛的血压影响进行了综述。可乐定或胍法辛引起的中枢α-肾上腺素能受体兴奋会同时导致外周交感神经张力降低、低血压和心动过缓。脑桥延髓区域和下丘脑都是这两种药物的重要作用部位。关于可乐定或胍法辛对中枢α-肾上腺素能受体的作用，研究了两种可能性。首先，我们推测这两种药物引起的中枢α-肾上腺素能受体兴奋似乎位于突触后部位。因此，考虑了α2亚型。其次，不能完全排除可乐定或胍法辛对中枢突触前α2受体的刺激作用。据报道，胍法辛突然停药后，很少会出现戒断综合征，与可乐定突然停药引起的戒断综合征相比，症状较轻。与可乐定相比，胍法辛的药代动力学特征，包括分布容积大、生物半衰期长和作用持续时间长，似乎与胍法辛停药后戒断综合征的罕见发生有关。
