KETAMINE: a pre-medication for anaesthesia. It can cause hallucinations, out-of-body experiences, unstable emotions and irregular heartbeat, and impair balance and muscle co-ordination. Used over several months, it can damage brain cells, reduce concentration and impair memory.

ECSTASY: developed from amphetamine. It can intensify perception of sounds and colours, lead to nerve cell damage, cause high fevers and dehydration. It increases the heart rate and raises blood pressure, with risk of stroke and paralysis. Prolonged use can cause mental illnesses.