Statins May Cause Muscle Damage in Some Patients

July 7 -- MONDAY, July 6 (HealthDay News) -- Statins, medications widely used to lower cholesterol, may cause structural damage to the muscles of people experiencing muscle aches and weakness, a new study has found.

The damage may occur even when tests for a protein thought to signal injury are normal, and may persist even after statin use is halted, according to the study in the July 7 issue of the Canadian Medical Association Journal.

The researchers stressed that people not experiencing significant pain had no cause for alarm and should continue taking the medicine.

About 10 to 15 percent of people taking statins report myalgia, or minor muscle aches and weakness, according to the study authors. A smaller number have stronger, persistent pain, called myopathy.

In the study, researchers biopsied leg muscle tissue from 83 patients: 44 were taking statins and had serious and persistent muscle pain; 19 were taking statins and had no myopathy, and 20 had never taken statins or suffered myopathy.

Of the 44 with myopathy, 29 were still taking a statin at the time of the biopsy, while 15 had discontinued their use for at least three weeks.

Biopsies showed that 25 of the 44 with myopathy had muscle damage, defined as injury to 2 percent or more of the muscle fibers.

Yet only one patient showed elevated levels of creatine phosphokinase (CPK), an enzyme expressed inside skeletal muscle cells, said study co-author Dr. Richard Karas, director of preventive cardiology at Tufts Medical Center in Boston.

Elevated levels of CPK in the blood can mean the enzyme is leaking out of the muscle cells, indicating muscle damage.

"This paper is challenging the dogma that if the CPK level is low, it rules out the possibility of muscle damage," Karas said. "You can have microscopic muscle damage and the level of CPK can still be normal."

The researchers also found that most participants showed signs of muscle injury even after they'd stopped taking statins.