June 9, 2011 -- The U.S. Food and Drug Administration has recommended limiting high doses of a widely prescribed cholesterol-lowering drug called simvastatin -- commonly known as Zocor -- after reviewing the results of a clinical trial that found a higher risk of muscle damage compared to patients taking lower doses of the statin.
The use of the 80-mg dose of Zocor, the highest approved dose of the drug, can harm muscles and potentially cause deadly kidney damage, the U.S. Food and Drug Administration warned Wednesday.
The new recommendation applies only to what the FDA estimates to be 2 million Americans who in 2010 were prescribed 80 milligram doses of simvastatin in one form or another -- whether as Zocor or its generic equivalent, or in the combination statin drugs Vytorin and Simcor.
The most common side effects of Zocor include muscle pain, tenderness and weakness. While rare, more serious side effects include muscle damage that can lead to liver disease and kidney failure. Five out of every 100,000 people taking Zocor for a year experienced the effects, according to the FDA.
Statins, including Zocor, have been shown to dramatically lower bad cholesterol in patients with heart disease and diabetes. But many doctors say they've known long before this warning of its potential dangers. And, some said, an FDA recommendation for a warning label is a necessary next step.
"It's about time," said Lynn Willis, professor of the department of pharmacology at Indiana University School of Medicine in Indianapolis. "I'm of the view that the muscle pain induced by Zocor occurs with much greater frequency than we would think."
Dr. Steven Nissen, chairman of the department of cardiovascular medicine at Cleveland Clinic referenced an editorial he wrote for the Journal of the American Medical Association in 2004 citing potential dangers of the high dose medication.
"It takes the FDA a long time to make these decisions," said Nissen. "Unfortunately it takes time to sort through the evidence."
Many doctors said they already switch to other kinds of statins, including Crestor and Lipitor, if a patient requires a higher dose. The drugs were not among those shown to raise the risk of muscle damage.
"The more we study drugs in a systematic fashion and conduct surveillance, the more we find out," said Dr. John McPherson, a clinical cardiologist at Vanderbilt University Medical Center in Nashville, Tenn.
McPherson is among many researchers at Vanderbilt who are looking into specific genes that can show if a patient is at risk for complications from Zocor before they are even put on the drug.
Many heart patients at Vanderbilt University Medical Center now undergo genetic tests before they are prescribed any kind of heart medications, including statins.
"An abnormal copy of the gene can affect how we metabolize drugs," said Dr. Russell A. Wilke, director of genomics and cardiometobolic risk at Vanderbilt University Medical Center. "We are using genetic tests to reduce the frequency of statin-related side effects.
"We can know at the point of prescribing," Wilke said, adding that doctors can get test results within 24 hours.
Doctors can also determine how a patient might react to high-dose Zocor by looking at other drugs a patient is taking, his or her age, and family history.
Only patients who have been taking the 80-mg dose for 12 months or longer without signs of muscle damage should continue to take Zocor, the FDA recommended.
Patients should not stop taking their medication unless told by a doctor to do so.
"Certainly, many of these patients will be cut down to lower dose to stay within guidelines," Vanderbilt's McPherson said. "We'll also consider moving to other statins that aren't as high risk."