Another class of drugs is often referred to as downers.
另一类毒品常常被称为镇静剂。
Drugs in this class can decrease the heart rate, make users sleepy and may give users an artificial sense of pleasure -- though this effect fades after a time.
这一类的毒品能够降低心跳速率，让吸食者感到困倦，并能让吸食者获得一种愉悦的幻觉——虽然这种效果稍纵即逝。
Downers are known to cause headaches, feelings of sadness and a weak pulse.
镇静剂据悉可以引起头痛，伤感和脉搏虚弱。
In some situations, using downers can lead to death.
在一些情况下，便用镇静剂可导致死亡。
An example of this type of drug is heroin, which is usually taken as a shot or is sniffed.
这类毒品的一个例子就是海洛因，它被用来注射或者吸食。
Heroin is one of the most powerful drugs in the world.
海洛因是世界上最强效的毒品。
Even a small amount of it is enough to slow the brain and the body's reactions, and heroin users usually become addicted and begin a downward slide after only a few uses of the drug.
即使少量的海洛因已足够降低大脑和身体的反映速度，而且海洛因吸食者能成瘾并且使用极少量毒品时就开始有所反映。
Alcohol is also classified as a downer, and although it is legal, it can damage the liver and do great harm if consumed in large quantities.
酒精也被归类到镇静剂，尽管它是合法的，但它会损害肝脏，如果大量饮用会产生巨大危害。