Ketamine is a drug that doctors and vets made to stop pain and to put a body to sleep for an operation. It works in a strange way: the person or animal may still have their eyes open, but they do not feel the cut, and they can feel far away from their own body. Hospitals and animal clinics still use it, especially when they need something that will not slow breathing as much as some other sleep drugs. That is the legal medical story. The other story is that some people take it at parties to get high — swallow, snort, or inject it. On the street it is often Special K, or just K. That use is illegal, and it can be dangerous: too much can leave you unable to move or look after yourself (a very deep trip is a K-hole), and using it a lot can hurt the bladder. So the same substance sits in two worlds — a tool in a clinic, and a banned party drug. It is not vitamin K, and it is not the K that means potassium on a food label. Those are different Ks.