Amphetamines, which can come in pill, capsule or powder form, stimulate the heart beat and may increase blood pressure.

Users say they experience feelings of increased confidence, sociability and energy. The effects usually kick in about half an hour after taking the drug and last for several hours. As the effects wear off, users may feel irritable, restless, dizzy and anxious.

Insomnia is very common, as is depression. Increased blood pressure can cause burst blood vessels and may, in rare cases, lead to paralysis and coma. Some people suffer a bad or toxic reaction to even low doses of amphetamines. Tolerance builds up with regular use so more of the drug has to be taken to get the same effect. This can lead to dependence.

Withdrawal symptoms include depression, lethargy, heart palpitations, chills and headaches. Excessive sweating and dehydration are common. High doses or particular reactions to the drug can be fatal due to the increased risk of convulsions, coma and brain haemorrhage. Regular, heavy use of amphetamines can cause hallucinations, paranoia, brain damage and mental illness.

Pregnant women who regularly use amphetamines may suffer premature birth and the drug can be passed onto babies through breast milk.