sedative

a. 使安静的,使镇静的
n. 镇静剂,能使安静的东西

The doctor gave him a sedative to help him sleep.

医生给了他镇静剂帮助他入睡。

I've given him a sedative; that should see him through the night.

我给了他一片镇静剂，可使他熬过一个夜晚。