Statin's long-term effects continue after stopping the drug

Cholesterol-lowering statin drugs may cause serious and long-term muscle damage that persists even after the drugs are halted, according to a new study published in the Canadian Medical Association Journal.

Researchers have known for some time that minor muscle aches and weakness, known as myalgia, occur in between 10 and 15 percent of patients taking statins, while more severe, persistent pain known as myopathy occurs in roughly 2 percent. In the current study, researchers performed muscle biopsies on 83 patients, 44 of whom were taking statins and also suffering from myopathy severe enough to interfere with exercise and daily activities. Twenty-nine of these patients were currently taking statins, while the other 15 had ceased using the drugs at least three weeks before.

Another 19 participants were taking statins but not suffering from myopathy, while the final 20 had never experienced myopathy and never taken statins.

Researchers found signs of muscle damage in 25 of the myopathy patients, including the majority of those who had already stopped taking statins.

"Although in clinical practice, the majority of patients with muscle symptoms improve rapidly after cessation of therapy, our findings support that a subgroup of patients appears to be more susceptible to statin-associated myotoxicity, suffering persistent structural injury," said senior author Annette Draeger.

The researchers also found that only one of the patients with muscle damage had elevated levels of the enzyme creatine phosphokinase (CPK), widely believed to be a marker of muscle distress.

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