Federal drug safety reviewers are calling for limits use of the highest dose of the cholesterol drug simvastatin, which is most commonly marketed as Zocor, saying that the 80 mg version carries an increased risk of muscle injury.
The FDA announced this week that it has completed a safety review of Zocor, and is recommending that no new patients be started on an 80 mg simvastatin regimen, due to the risk of myopathy and rhabdomyolysis; rare forms of muscle injury.
The Zocor drug safety communication also contains a list of drugs that should not be used in combination with Zocor, including the combination cholesterol drugs Vytorin and Simcor.
The FDA began reviewing the side effects of Zocor in March 2010, when it first warned of the possible increased risk of rhabdomyolysis and other muscle injuries.
According to the agency, about 4.9 out of every 100,000 people who are on an 80 mg Zocor prescription will be hospitalized for rhabdomyolysis, particularly within the first year of taking the drug, when the risk is highest.
As a result of its findings, the FDA is recommending that 80 mg Zocor only be given to people who have already used it for a year or more without problems. The agency is asking doctors not to start any new patients on doses that high. If patients do not achieve cholesterol control on 40 mg Zocor, FDA experts urge doctors to try them on another treatment instead of upping the dosage.
Zocor (simvastatin) is a synthetic statin developed by Merck & Co., which is also widely available as generic simvastatin. Before patent protections expired in 2005, it was Merck’s best-selling drug and the second best selling cholesterol lowering drug in the world, bringing in $4.3 billion in 2005.
Rhabdomyolysis from Zocor causes muscle fibers to begin to break down, releasing a protein called myoglobin, which can damage the kidneys as they attempt to filter it out of the bloodstream. Symptoms of rhabdomyolysis include muscle cramps, tenderness, stiffness, pain or spasms. The illness is usually reported in patients over 65 years of age or those who have renal impairment or uncontrolled hypothyroidism.
All statins have been found to carry a risk of muscle injury, known as myopathy, and rhabdomyolysis is the most severe form, potentially causing severe kidney damage, kidney failure and death. All statins currently contain a warning that myopathy and rhabdomyolysis are rare possible side effects.
Statins are among the best-selling drugs in the United States, with $14.5 billion in combined sales in 2008. They use the liver to block the body’s creation of cholesterol, which is a key contributor to coronary artery disease. Statin is used in a number of other popular cholesterol controlling drugs, including Crestor, Lipitor, Mevacor, Lescol and Pravachol.