Britain's drug regulator has announced that certain antidepressants should not be prescribed to children because they could make young patients suicidal.
The Medicines and Healthcare Products Regulatory Agency said on Wednesday a study of evidence from drug companies concluded that the risks to those under 18 posed by selective serotonin reuptake inhibitors (SSRIs) outweighed the benefits.
Of this type of drug, only fluoxetine, marketed as Prozac, is not included in the warning, the agency said.
The drugs are not licensed for use by under-18s, but an independent advisory group said it was known that some doctors had independently decided to prescribe them to children.
The Department of Health said on Wednesday that 30,000 to 40,000 children and teenagers were prescribed SSRIs in the UK and about half of those were treated with Prozac.
The regulatory agency said side effects had been shown to include suicidal feelings, anxiety, insomnia, weight loss and headaches.
In October, the US Food and Drug Administration issued a health advisory alerting doctors to a possible link between antidepressant drugs and suicidal feelings in young people.
Prozac is the only drug approved in the US for treatment of major depressive disorders in children.
Alasdair Breckenridge, chairman of the British agency, warned that patients on SSRIs should not suddenly stop taking them, but should talk to their doctor about treatment.
The drugs specified in the government announcement were sertraline (marketed in the UK as Lustral, and in the US as Zoloft), citalopram (Cipramil or Celexa), escitalopram (Cipralex or Lexapro) and fluvoxamine (Favarin or Luvox). Earlier this year, warnings were also issued on the risks of paroxetine (Seroxat or Paxil) and venflaxine (Efexor or Effexor).
The regulatory agency said that this left only fluoxetine (Prozac), which appeared to have "a positive balance of risks and benefits" in treating under-18s.
Professor Gordon Duff, chairman of the independent advisory Committee on Safety of Medicines, said it had issued comprehensive advice on the use of these drugs for children after a thorough review of all the evidence available.
"This gives parents, young people and those who treat these devastating illnesses the information they need to make informed decisions about treatment," he said.
"None of these drugs has ever been licensed for use in those under 18," he said.
"We know, however, they are used in this age group outside of their licensed indications where prescribers make a judgement on their own responsibility that it is the correct treatment for a particular patient," he said.
The regulatory agency said it was going to release data from clinical trials on SSRIs and children which had been supplied by drug companies to allow doctors to assess the information on which the advice was based.
The expert group is continuing to focus on the safety of the drugs in adults.
Professor Ian Weller, chairman of the working group, said there was no evidence to suggest the risk of treatment outweighed the benefits for adults.
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