20 Mar 2010
Simvastatin is taken by around three million people in order to lower their cholesterol and reduce the risk of having a heart attack.
However an analysis of clinical trial data in America has found that high doses can cause muscle damage and a rare condition which induces kidney problems and may be fatal.
Patients were told not to stop taking simvastatin but advised to talk to their doctor if they have concerns.
The American medicines regulator, the Food and Drug Administration, has issued a warning to patients to be alert to signs of problems when taking the 80mg daily dose of simvastatin. It has also listed drugs that should not be prescribed to those on high doses of statins.
Muscle aches and damage are a known side effect of all statins but the risks are generally considered to be outweighed by the benefit in reducing the risk of a heart attack.
The FDA found that patients on the 80mg dose were more likely to develop a severe form of muscle damage called myopathy, compared with those on the lower 20mg dose.
Over six years, 52 of the 6,031 patients taking 80 mg doses developed myopathy compared with one person out of the 6,033 taking 20mg.
And 11 patients taking the 80 mg dose developed rhabdomyolysis, the most serious form of myopathy which can lead to kidney failure and death, where as none of those on the 20mg dose developed the condition.
The majority of patients in Britain taking simvastatin are on the 20mg and 40mg dose.
The FDA said patients experiencing muscle pain, tenderness or weakness, urine that is dark or red-coloured, or unexplained tiredness, should contact their doctor.
The UK drugs regulator said the side effects are known about and included in patient information with the medication.
A spokesman for the Medicines and Healthcare products Regulatory Agency said: "The 80 mg per day dose is only recommended in patients with severe hypercholesterolaemia and at high risk for cardiovascular complications.
"Myalgia (complaints of muscle aches) is a common side effect of statins, including simvastatin. It is recognised that very rarely statins can cause more serious muscle damage (myopathy) which in some cases may be life-threatening.
"There are comprehensive warnings in the product information for prescribers and in the Patient Information Leaflet.
"These warnings advise that the risk of muscle injury is greater: at higher doses of simvastatin; when used in combination with certain other medicines including amiodarone (a medicine used for an irregular heart beat) and other medicines that are recognised to increase the risk of myopathy; and in certain patient groups including those who are more than 70 years old, those with kidney or thyroid problems, those who consume large amounts of alcohol, and those with a history of previous muscle problems during treatment with statins or other lipid lowering drugs.
"As with all marketed medicines the safety of simvastatin is kept under continuous review by the MHRA."
Ellen Mason, Senior Cardiac Nurse at the British Heart Foundation (BHF) said: “Simvastatin remains a widely used and well researched drug, which has been around for many years and serious muscle damage is rare.
"It is considered a safe drug for many people in the UK to take. The benefits of statins in lowering cholesterol levels and reducing the risk of a heart attack are clear.
“Only a small number of people with very high levels of cholesterol would need to take the maximum dose of simvastatin. Any concerned patients who are taking the highest prescribed dose and experience muscle weakness or pain should speak to their GP.”