Lower Zocor Doses Needed To Avoid Side Effects, UK Regulators Warn

Regulators in the U.K. are cutting simvastatin doses for some patients in half, indicating that it is the only way to mitigate some of the potential side effects of Zocor at high doses, while still leaving the cholesterol drug at useful levels for patients. 

The Medicines and Healthcare products Regulatory Agency (MHRA) issued a safety warning for Zocor (generic simvastatin) on October 29, alerting some patients that their dosages were being reduced in order to help avoid the risk of a severe muscle injury.

The MHRA says that patients taking some other drugs, such as amlodipine and diltiazem, can be at increased risk of muscle damage due to the combined effects of the drugs. Their doses are being cut from 40 mg to 20 mg.

Zocor (simvastatin) is a synthetic statin developed by Merck & Co., which is widely available as generic simvastatin. 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.

While all statins have been associated with an increased risk of muscle injury, high doses of Zocor have been linked to a particularly high risk, which has already resulted in major dosing reductions in the U.S.

In June 2011, the FDA placed restrictions on the use of 80 mg Zocor, which could include twice-a-day 40mg doses, due to the risk of myopathy and rhabdomyolysis, a potentially life-threatening muscle injury.

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.

The FDA had a restriction even more restrictive than the one announced by the MHRA on the use of Zocor for patients taking the heart drug amiodarone, restricting amidarone-using patients to 10 mg of Zocor per day. However, the agency relaxed the restriction in December 2011, increasing the dosage to 20 mg per day, the same as the new MHRA limit.

A number of individuals throughout the United States who have been diagnosed with rhabdomyolysis after taking high doses of the medication are now pursuing a Zocor lawsuit, alleging that Merck concealed information about the risk of muscle injury from the medication and failed to warn doctors and plaintiffs of the potential side effects of simvastatin.