Ketamine is a dissociative general anaesthetic, classed as a hallucinogen when used illegally as a recreational drug. Doctors and vets use ketamine because it produces analgesia (pain relief) and amnesia. It is also sometimes described as a horse tranquiliser due to its use in veterinary medicine. When sold illegally, ketamine usually comes as a white crystalline powder, but it can also be made into tablets or dissolved in a liquid. It is usually snorted through a small glass nasal inhaler (a ‘bumper’), but can also be swallowed, smoked or injected...