α-肾上腺素能受体阻断剂是众多降压药物中的一大类。其中最早发现的药物是哌唑嗪,尽管它对某些病例效果相当好,但有明显的首剂效应。这种较严重的副作用使许多高血压患者不敢使用。乌拉地尔(Urapidil)是与其很相似的药物,药效学也基本类似,均通过减小周围血管的阻力来降压。不同的是,乌拉地尔比哌唑嗪更着重作用于静脉血管,而不是动脉系统。这就很可能使乌拉地尔的首剂效应相应减轻。 Alpha-adrenergic receptor blockers are a large group of many antihypertensive drugs. The earliest drug found was prazosin, which, although it worked quite well in some cases, had a clear first-dose effect. This more serious side effects make many hypertensive patients afraid to use. Urapidil is a very similar drug with a similar pharmacodynamic profile and is depressurized by reducing the resistance of the surrounding blood vessels. The difference is that Urapidil is more pirazine acting on the veins rather than on the arterial system. This is likely to reduce the first-dose effect of Urapidil.