根据《柯林斯英汉双解大词典 》：
N-COUNT A tranquilizer is a drug that makes people feel calmer or less anxious. Tranquilizers are sometimes used to make people or animals become sleepy or unconscious. 镇静剂[1]
Injection tranquilizer 镇静剂注射
sedative tranquilizer 镇静剂
major tranquilizer 强安定药 ; 重安神剂
Administration tranquilizer 镇静剂投药
strong tranquilizer 强镇静剂
Tranquilizer Dart 麻醉镖
horse tranquilizer 马安定剂
ataractic tranquilizer 安定剂
minor tranquilizer 弱安定剂 [1]
If a tranquilizer is prescribed, be sure your physician informs you of its possible side effects, such as addiction.
如果开了镇静剂，一定要让医生告诉你它可能带来的副作用，例如上瘾。
Pic.15 A tiger with a tranquilizer dart stuck in its back walks inside the Assam State Zoological cum Botanical Garden in Guwahati January 30, 2010.
图15 2010年1月30日，在高哈蒂的阿萨姆省动植物园，一只被麻醉镖扎中背部的老虎在走动。