Horse tranquilizer is a dangerous and illegal substance that is used to sedate horses, and unfortunately it is also abused by humans. There are many different terms referring to this substance, and it is important to be aware of them in order to understand conversations about drug abuse. Some synonyms for horse tranquilizer include ketamine, Ket, Super C, Special K, and Vitamin K. When used illegally, this substance can cause serious physical and mental harm, including addiction, hallucinations, seizures, brain damage, and overdose. It is important to seek help if you or someone you know is struggling with substance abuse of any kind.