A drug charity in Britain says increasing numbers of drug users are turning to the tranquilliser Valium (diazepam) as a substitute for heroin.
The charity DrugScope provides online information on drugs and aims to provide quality drug information in order to reduce drug-related harm to individuals, families and communities.
A survey by DrugScope has found that the use of Valium is on the rise among drug users in at least 15 towns and cities as a heroin substitute, and is often taken along with alcohol and methadone to ease the comedown from crack cocaine.
The annual survey by the charity questioned 100 drug services and police forces in 20 towns and cities across the UK.
DrugScope warns that combining Valium with other drugs greatly increases the risk of overdose and is reportedly harder to give up than heroin.
In the UK, Diazepam is a Class C drug prescribed to reduce anxiety and tension and legally is only available on prescription.
DrugScope says Valium has a street name of "blues" or "vallies" and a 10mg tablet is available for £1.
Its relative low cost, easy accessibility and a reduction in the availability of good quality heroin, have all contributed to Valium's increased popularity.
DrugScope says an unexpected heroin shortage has occurred despite the bumper harvest in Afghanistan and diazepam from legitimate sources in Europe is being smuggled into Britain.
It is also being bought over the internet from India, Pakistan and Thailand, some of which warns Drugscope, is counterfeit.
Between July 2003 and June 2006, 300,000 diazepam pills were seized by police and customs, but in the period between July 2006 and June 2008 seizures rose to two million.
Drugscope says mixing diazepam with other drugs, especially alcohol, is a "potentially lethal combination", the drug is also highly addictive and withdrawal can take months.
DrugScope said "poly" drug use where a combination of drugs such as alcohol, cannabis, cocaine and ecstasy is used, was a significant problem among some young people.
DrugScope says cocaine was still popular, with a "two-tier" market in which low quality powder was sold for less than higher quality powder and in the ecstasy market, there was an increase in the amphetamine-like drug N-benzylpiperazine (BZP) replacing Methylenedioxymethamphetamine (MDMA) as the ingredient in pills.
The Advisory Council on the Misuse of Drugs is considering the drug BZP in order to provide advice to the government on its classification.
DrugScope also found that in many areas, young Class A users who could not afford heroin or cocaine at any one time were turning to alcohol such as super-strength lager, cheap vodka and cheap white wine.