David Prout says the appetite-suppressant drug has helped him lose weight
The European drugs watchdog is recommending doctors do not prescribe the anti-obesity drug rimonabant, also known as Acomplia.
The European Medicines Agency has said the risk of serious psychiatric problems and even suicide are too high.
The EMEA says since at-risk patients cannot be identified, marketing of the drug should be suspended.
Patients taking the drug should consult their doctor, but do not need to immediately stop taking the medication.
Around 97,000 people in the UK who are obese or overweight have been prescribed rimonabant, which is used in conjunction with diet and exercise.
And approximately 20,000 are currently taking the drug.
It was approved for use by the NHS watchdog in England and Wales in June this year.
Patients who are currently taking Acomplia should consult their doctor or pharmacist at a convenient time to discuss their treatment
There have always been concerns over the risks of depression and suicide associated with the drug, and in July last year, the EMEA warned it may be unsafe for patients also taking anti-depressants.
Doctors were also told not to give it to patients with a history of major depression, and to be alert for new symptoms of depression in patients taking the drug.
But data from more recent studies, and from Sanofi-Aventis itself, has shown there is around double the risk of psychiatric disorders in obese or overweight patients taking rimonabant compared to those taking dummy pills.
And between June and August 2008, there were five suicides among patients taking part in a trial who were on the drug, compared with one among those taking the dummy version.
The EMEA's Committee for Medicinal Products for Human Use, which assessed the new evidence, also said that the drug was less effective in reality than clinical trials had suggested, as patients only tended to take it for a short period.
The EMEA said in a statement: "Prescribers should not issue any prescriptions for Acomplia [rimonabant] and should review the treatment of patients currently taking the medicine.
"Patients who are currently taking Acomplia should consult their doctor or pharmacist at a convenient time to discuss their treatment.
"There is no need for patients to stop treatment with Acomplia immediately, but patients who wish to stop can do so at any time."
My patients were doing very well on it, and they will now have to stop and come off it
Dr Colin Waine, National Obesity Forum
Dr June Raine of the UK's Medicines and Healthcare products Regulatory Agency (MHRA) backed the EMEA's advice.
Professor Steve Field, chairman of the Royal College of GPs, said he was not surprised by the decision.
"I was concerned when the drug was first approved, so I support the EMEA."
In a statement, Sanofi-Aventis said it would comply with the EMEA's decision, but that it believed rimonabant would remain "an important therapeutic answer to a highly prevalent and increasing unmet medical need".
Dr Colin Waine, chairman of the National Obesity Forum, said: "My patients were doing very well on it, and they will now have to stop and come off it."
"Patient safety must be foremost, but I always thought that if you ruled out the patients with depression, you ruled out the problem with the drug."
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