FOR some, it is a "chemical cosh", dished out by doctors likes Smarties. For others, it has transformed their lives, allowing them to live normally.

Parents of hyperactive children who consider Ritalin nothing less than a wonderdrug have welcomed new guidelines published yesterday by the National Institute for Clinical Excellence (Nice). After years of controversy, they set out who should be prescribed the drug on the NHS.

Ritalin is used to treat Attention Deficit Hyperactivity Disorder (ADHD), which causes severe impulsive behaviour, and Attention Deficit Disorder (ADD) which makes sufferers dreamy and inattentive. About three per cent of the population, mainly children, have one of the conditions.

As diagnosis rates of the conditions have increased in recent years, so have prescriptions for Ritalin (methylphenidate hydrochloride). In the US, four million children take Ritalin, while last year 157,900 prescriptions were written for the class B drug in the UK. Although it has a similar effect to cocaine and is chemically similar to amphetamines like speed, it calms patients.

Caroline Hensby, a 37-year-old mother of three from Kent, who has ADD and a teenage son with ADHD, runs a support group for the condition. She believes Ritalin has transformed both their lives. But not everyone supports the use of Ritalin; some parents claim it has turned their youngsters into "monsters". In the US, parents are taking legal action against Ritalin manufacturers, Novartis Pharmaceuticals, alleging the company failed to warn about the drug's possible impact on children's cardiovascular and nervous systems.

Janice Hill from the support group Overload, which campaigns against over-prescription of drugs, said: ''The guidance does not even mention the legal action taking place in the US, and it relies on a study which was sponsored by drugs companies.''

More than 70,000 children aged six-16 in England and Wales meet the diagnostic criteria for ADHD, and around 48,000 do not currently receive Ritalin.

The new guidelines say that a comprehensive treatment programme for children who are diagnosed with ADHD should be set up. Youngsters on the drug should be regularly monitored and if their condition stabilises the drug should be withdrawn.