The MHRA has advised GPs to stop prescribing the drug and to review the treatment of patients taking it. Pharmacists are being asked to cease dispensing it.
People on sibutramine should make a routine appointment with their doctor to discuss alternative measures, the MHRA said. But there are no health implications if people wish to stop treatment before seeing their doctor, the agency added.
Last year, 86,000 people were prescribed sibutramine on the NHS. Sibutramine's European licence was suspended after the European Medicines Agency (EMEA) concluded that the drug was associated with an increased risk of non-fatal heart attacks and strokes.
Clinical director of the National Obesity Forum Dr David Haslam, a GP in Hertfordshire, said he was 'disappointed and surprised' by the decision.
Those no longer treated with sibutramine would gain weight and face increased risk of vascular complications, he said.
Patients given the drug would have already failed to lose sufficient weight through diet and exercise and orlistat treatment, he added. He hoped detailed analysis of the safety data would enable the drug to be relicensed.
Dr Peter Stott, a GP in Surrey with an interest in obesity, said that although weight loss drugs showed modest benefits, they helped motivate patients to lose weight. 'It's sad that it's been withdrawn,' he said.
Reductil's manufacturer Abbott has contested the EMEA's assessment of sibutramine's safety. 'We believe there are many patients who benefit from sibutramine,' a spokesman said.