Federal regulators warned today against taking the highest approved dose – 80 mg – of the statin Zocor (simvastatin). According to the Food & Drug Administration (FDA) the high dose has been associated with a higher risk of serious muscle injury, called myopathy, and a disorder called rhabdomyolysis.
The agency’s warning was based on its review of data from a large clinical trial called the Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine (SEARCH) trial, as well as data from other clinical trials, observational studies, adverse event reports, and data. The SEARCH trial evaluated over 6.7 years the number of major cardiovascular events (heart attack, revascularization, and cardiovascular death) in 6031 patients taking 80 mg of Zocor compared to 6033 patients taking 20 mg of the medication. All patients in the study had previously had a heart attack.
Of the study patients given the highest dose of Zocor, 52 (.09 percent) developed myopathy, while only one patient (.02 percent) in the 20 mg dose group did so. The FDA’s preliminary analyses of the primary data suggest that 11 (0.02%) of the patients in the simvastatin 80 mg group developed rhabdomyolysis compared to no patients in the simvastatin 20 mg group.
Myopathy is a known side effect with all statin medications. According to the FDA, the risk of myopathy is also increased when Zocor, especially at the higher doses, is used with certain drugs. Those drugs include amiodarone, niacin and diltiazem.
The most serious form of myopathy is called rhabdomyolysis. According to the FDA, it occurs when the protein myoglobin is released as muscle fibers break down. Myoglobin can damage the kidneys as they filter blood out of the body. Patients with rhabdomyolysis may have dark or red urine and fatigue, in addition to their muscle symptoms. Damage to the kidneys from rhabdomyolysis can be so severe that patients may develop kidney failure, which can be fatal.
According to the FDA, known risk factors for developing rhabdomyolysis include age (> 65 years), low thyroid hormone levels (hypothyroidism), and poor kidney function. Myopathy and rhabdomyolysis are listed as possible side effects in the simvastatin and other statin drug labels.