Federal drug regulators are reversing themselves on the maximum dose limits placed on the cholesterol drug Zocor when it is used with the heart medication amiodarone, saying the scientific evidence does not back up the restrictions put in place earlier this year.
The FDA issued a Zocor drug safety communication on December 15, announcing that it was changing the maximum recommended dosage for Zocor from 10 mg to 20 mg when used with amiodarone.
In June, the FDA placed restrictions on the use Zocor, due to the risk of myopathy and rhabdomyolysis, a potentially life-threatening muscle injury. At that time, the agency indicated that doctors should no longer prescribe Zocor 80mg doses, which could include twice-a-day 40 mg doses, and also indicated that no more than 10mg of Zocor should be used with amiodarone, a generic heart drug sold under a variety of brand names, including Cordarone, Pacerone and Nexterone.
In the update released this week, the agency now indicates that the 10 mg is not justified, but that the overall daily dose limits for Zocor are appropriate.
Zocor (simvastatin) is a synthetic statin developed by Merck & Co., which is widely available as generic simvastatin from a number of different drug makers, including Dr. Reddy’s. 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.
“Unlike other interacting drugs, there were no pharmokinetic or clinical trial data to support the simvastatin dose reduction approved with amiodarone,” the FDA announcement states. “Therefore FDA has determined that the simvastatin dose limitation, when taken with amiodarone, should be restored to 20 mg.”
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.