GPs should switch all patients taking simvastatin 40mg and amlodipine to a lower dose of statin, or another statin altogether, because of the risk of muscle damage, recommends the medicines regulator.
The warning from the Medicines and Healthcare products Regulatory Agency - issued in its August drug safety update - changes the dosage recommendations for simvastatin, with those patients taking the cholesterol-lowering drug in conjunction with diltiazem or amlodipine to only be given the maximum dose of 20mg a day.
The latest update from the agency also warns that simvastin is now also contraindicated with ciclosporin, danazol and gemfibrozil.
The dosage change and additional contraindications are due to recent analysis of clinical trial data which found that‘theseinteractions may increase plasma concentrations of simvastatin which is associated with an increased risk of myopathy and/or rhabdomyolysis', according to the MHRA.
The changes come after the MHRA issued a warning in May 2010 about the increased risk of myopathy which was associated with the use of high-dose simvastatin of 80mg a day.
The dosage change is expected to have a big impact on GPs and their prescribing, with NICE currently recommending generic simvastatin 40 mg daily as the first-choice drug for primary prevention of cardiovascular disease.
Dr John Allingham, a GP in Dover and medical secretary at Kent LMC,said that 40mg was the ‘standard dose' for primary prevention and the move would affect many of his patients being treated for hypertension.
‘Practices will have to identify their patients, write to them and then change them over,' he said. ‘I think most GPs will change them over to atorvastatin instead.
Dr Terry McCormack, a GP in Whitby, North Yorkshire, said he was surprised at the recommendations: 'I would have thought that it is very commonly used with that dose and I am not aware of a large upsurge in cases of rhabdomyolysis.
'Amlodipine is such an excellent antihypertensive that it will continue to be commonly prescribed. We will just need to use different statins with it. Now that atorvastatin is off patent it will undoubtedly become the most commonly used statin.'