The FDA ( Food and Drug Administration ) has informed the public that it has revised the dose limitation for the cholesterol-lowering drug Simvastatin from 10 mg to 20 mg when it is co-administered with the cardiac drug Amiodarone ( Cordarone ).
In June 2011, FDA previously recommended that the dose limitation for Simvastatin be decreased from 20 mg to 10 mg, and has now reconsidered that recommendation.

In patients who are taking both Simvastatin and Amiodarone, the dose of Simvastatin should not exceed 20 mg per day. The Simvastatin drug labels ( Zocor and generics, Vytorin ) have been updated to reflect this correction.

In June 2011, FDA restricted the use of the highest approved dose of Simvastatin ( 80 mg ) to reduce the risk of muscle injury ( myopathy ). Therefore the 40-mg dose became the maximum safe dose of Simvastatin. At the same time, FDA also proportionally lowered ( i.e., a 50% reduction or more ) all the maximum safe doses of Simvastatin when it is taken with certain interacting drugs ( i.e., drugs that can raise Simvastatin blood levels ). However, the Simvastatin dose limitation when taken with Amiodarone ( in which the Simvastatin dose was lowered from 20 mg to 10 mg ) was made in error. Unlike other interacting drugs, there were no pharmacokinetic or clinical trial data to support the Simvastatin dose reduction approved with Amiodarone. Therefore FDA has determined that the Simvastatin dose limitation, when taken with Amiodarone, should be restored to 20 mg.

Source: FDA, 2011

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