Ketamine

Also called K, ket, special K, vitamin K, cat valium.

Originally developed as a general anesthetic for humans but is now mostly used in animal medicine.
Can be sold as a liquid, capsules, or crystal and is often distributed as a white powder.
Colourless, odourless, tasteless, and can easily be dissolved in a drink.
Difficult to know the exact strength of the drug or if it has been cut with dangerous chemicals, especially when buying from an unfamiliar supplier.
Taken with other drugs, including alcohol, greatly increases the risk of overdose and death. Boosting (taking more while already high) is even riskier.
Little is known about the long-term effects of regular ketamine use. Any drug can be addictive and have very negative effects.

Effects

Begins with a rush (within 5–20 minutes) and can last for about an hour depending on dose
Users report feeling relaxed and sedated
Music may seem louder, but ketamine "shuts off" the ability to hear certain kinds of sounds
Tastes and smells are decreased
Feeling removed from the body
Confusion, chaos, blackouts
Difficulty moving or speaking
Inability to see or hear others (the "K-hole")
Powerful hallucinations or Near Death Experiences (NDE)
Nausea and vomiting
Breathing problems or racing heart
Death

The only way to stay completely safe is not to take ketamine.

Effects depend on the amount taken. It may reduce ability to sense danger. A safe environment with trusted friends can reduce this risk.
Small amounts can result in a loss of attention span, learning ability and memory.
Larger doses can cause delirium, amnesia, high blood pressure, depression and breathing problems.
Overdose will cause unconsciousness or possibly heart failure or death. Mixing with other drugs increases this risk.
It can reduce your ability to feel pain or know that you are hurt. A "sober sitter" can watch out for their friends.
Railing (snorting) increases chances of damaging the inside of the nose, or infection.
Because it works quickly, is odourless, tasteless, colourless, and can be dissolved in a drink, ketamine has been abused as a rape drug.
Driving a vehicle when taking ketamine is always dangerous.

Adapted with permission from the Designer Drug Harm Reduction Action Group, Hamilton, Ontario.