The cholesterol lowering drug is Zocor, also known as simvastatin.
The FDA is warning doctors and patients to limit the use of the highest dose of the generic and Zocor brand versions.
There is concern about an increased risk of muscle damage.
The FDA issued an alert in March and was investigating. It now says simvastatin 80 milligrams should not be started by new patients. That includes patients already taking lower doses of the drug.
Also, the FDA is requiring changes to the simvastatin label to show dosage recommendations and to say it should not be used with certain medications.