Although Wings hated how tired ketamine left her, she liked the highs too much to stop. When she was 12, Wings admitted to a family friend that she was using it.

Her family took swift action, transferring her to Christian Zheng Sheng College, a rehabilitation school and home for youth, where she was forced to cut ties with her drug friends.

When she saw the result of her brain scan - which showed a small, dark hole had formed at the base of her brain - she was alarmed.

'I had heart and lung problems too,' she says.

'Ketamine works very fast. I'd only been seriously taking it for a year at this point.'

Ketamine is one of the government's biggest headaches. Each year, the government spends more money on prevention campaigns, policing efforts and treatment centres.

There are numerous sub-committees and community outreach programmes, so one would assume the situation is improving.

Not quite. Reported drug use decreased briefly from 1996 to 2000, but has crept back up since. The rise in ketamine use is particularly disturbing. The Narcotics Bureau found the number of reported ketamine users under 21 had almost doubled between 2005 and 2008.

For many young people, 'taking ketamine is like drinking soda or eating candy,' says Alman Siu-cheuk Chan, principal of Christian Zheng Sheng College.

Dr Chan thinks the rise is an inevitable result of growing up in a wealthy society.

'In wealthy societies, young people don't have to worry about making a living ... they only have to go to school. They're easily bored and will try anything.

'Back in my days, if people didn't like school they could just quit and find a job,' he recalls. 'Children often had to make money to help the family. We couldn't afford to be irresponsible.'

But this year the government will take a different approach to fighting the war on drugs, says Ben Cheung Kin-leung, chairman of the Narcotics Bureau's Subcommittee on Treatment and Rehabilitation, Action Committee Against Narcotics (Acan).

More attention will be given to young people who have tried ketamine but are not yet regular users - a tactic known as secondary prevention.

Mr Cheung also hopes the government will help fund a specialised brain scan, which can catch areas of brain erosion due to drug abuse. It's the same scan that woke Wings up.

Side-effects

Ketamine use has three major side-effects, according to Dr Cheung:

1. brain erosion; impairs memory and function

2. deficiency in motor co-ordination, leading to problems like the shakes

3. kidney and urination problems

But Wings adds a fourth:

'It made me look really tired and old. I had lots of acne, deep eye bags and dark circles,' she says. 'You wouldn't recognise me in photos.'