The FDA cautions against high doses of Zocor (simvastatin), urges label changes

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The highest doses of the cholesterol-lowering drug Zocor produce an increased risk of muscle damage, the Food and Drug Administration cautioned Friday. The risk is highest in patients of Chinese descent and is also high when Zocor, known generically as simvastatin, is combined with certain other medications, including amiodarone, niacin and diltiazem.

All statins have a small but real risk of producing muscle damage called myopathy. In rare cases, this damage can progress to a more severe form called rhabdomyolysis, in which damaged muscle tissues release a protein called myoglobin into the bloodstream. Myoglobin can damage the kidneys, which filter foreign materials out of blood. Victims have dark or red urine and fatigue, in addition to muscle pain. The condition can lead to lethal kidney failure.

The damage is more common at the highest approved dose of Zocor, 80 mg. A large clinical trial comparing 6,031 patients taking 80 mg. daily with 6,033 patients taking 20 mg. found 52 cases of myopathy in the 80-mg. group and only one in the 20-mg. group. Eleven patients in the 80-mg. group developed rhabdomyolysis, but none in the low-dose group.

In 2008, the FDA cautioned against using doses of Zocor greater than 20 mg. in combination with the anti-arrhythmia drug amiodarone, sold under the brand names Pacerone and Cordarone. The agency has now approved new labeling for Zocor that warns against prescribing 80 mg. tablets of Zocor for patients of Chinese descent who are also taking cholesterol-lowering doses of niacin, and warns that physicians should carefully monitor such patients taking lower doses of Zocor. It is not known if the warning should apply to patients of other Asian descent.

The FDA also requested that Merck, which manufactures Zocor, change the labeling to warn physicians against prescribing doses of Zocor greater than 40 mg. to patients receiving the calcium-channel blocker diltiazem for high blood pressure.

For all patients, do not take simvastatin when using these drugs:

--itraconazole

--ketoconazole

--erythromycin

--clarithromycin

--telithromycin

--HIV protease inhibitors

--nefazodone

Patients should not take more than 10 mg. of Zocor daily with these drugs:

--gemfibrozil

--cyclosporine

--danazol

They should not take more than 20 mg. with these drugs:

--amiodarone

--verapamil

And they should not use more than 40 mg. with this drug:

--diltiazem

Simvastatin is also sold in a generic form, as well as in a combination with ezetemibe known as Vytorin and in a combination with niacin known as Simcor.

-- Thomas H. Maugh II

The cholesterol-lowering drug Zocor is one of the most popular prescription drugs in the United States. Credit: Mel Evans / Associated Press