High doses of the cholesterol-fighting drug Zocor can increase the risk of rhabdomyolysis, a serious and potentially fatal muscle disease, according to federal regulators.
The FDA released a Zocor rhabdomyolysis warning on March 19, as part of an ongoing investigation into the side effects of Zocor and other cholesterol medications that belong to a family of drugs known as statins. 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, however this is the first time the FDA has warned that the conditions may be dose specific.
Statins are 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.
Zocor (simvastatin) is a synthetic statin developed by Merck & Co., which is now available as a generic. 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.
The FDA’s drug safety communication warns that data from a large clinical trial indicates that the highest approved doses of Zocor, 80 mg, carry an increased risk of muscle injury over lower doses. Zocor rhabdomyolysis 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.
Zocor is also used in the combination cholesterol lowering drugs Vytorin (Exetimibe/simvastatin) and Simcor (Niaspan/simvastatin). Vytorin is produced and marketed as part of a joint venture between Merck & Co. and Schering-Plough, while Simcor is manufactured by Abbot Laboratories.
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.
The connection between Zocor, other statins and myopathy has been under investigation by FDA for some time. In August 2008, the FDA warned healthcare professionals not to administer more than 20 mg/day of simvastatin to patients receiving heart drugs containing amiodarune, such as Cordarone and Pacerone.
In addition, researchers from Europe warned last month that statins can increase the risk of diabetes. University of Glasgow scientists analyzed the results of 13 different studies into the side effects of statins and found that people using the cholesterol drugs faced a 9% increased risk of being diagnosed with type 2 diabetes.
The FDA recommended that patients not stop taking Zocor unless told to by their health care professional. They should contact their doctor if they experience muscle pain, tenderness or weakness, dark or red-colored urine or unexplained tiredness.