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
noun [物质名词]镇定剂;使镇定的人或物
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。