She's on (= is taking) tranquillizers.

她在服用镇静剂。

牛津词典

Sex is safest tranquillizer in the world.

性爱是世界上最安全的镇定剂.

期刊摘选

The patient is verry worried, so the doctor gives him a shot of tranquillizer.

由于病人烦躁不安, 医生为他打了一针镇静剂.

期刊摘选

Use as in pharmacy industry synthetic tranquillizer and anaesthetic.

在制药工业中用作合成镇静剂和麻醉剂.

期刊摘选