NEW YORK (Reuters Health) – Muscle pain and weakness in patients taking statins often reflect true muscle damage, new research shows.

Moreover, real muscle injury may exist even if circulating levels of creatine phosphokinase are not markedly elevated, Dr. Markus G. Mohaupt, from the University of Bern, Switzerland, and co-researchers report in the July issue of the Canadian Medical Association Journal.

The results stem from a study of 83 subjects who underwent biopsy of the vastus lateralis muscle, including 20 individuals who had never taken statins and 19 current statin users with no muscle complaints. The remaining 44 subjects were current or former users with muscle pain, weakness, or both.

Structural muscle injury was defined as damage of 2% or more of the muscle fibers in the biopsy sample, the researchers note.

Statin-associated structural muscle damage was found in 45 patients, including all 29 current users with myopathy, all 15 former users with myopathy, and one current user who had neither muscle pain nor weakness.

A single patient with muscle injury had a significantly elevated creatine phosphokinase level.

Elevated expression of ryanodine receptor 3 correlated with structural muscle damage, the authors note. This finding, they add, “is suggestive of an intracellular calcium leak.”

“Although muscle symptoms typically improve rapidly after stopping statin therapy, our findings suggest that some patients are more susceptible to statin-associated myotoxicity and persistent structural injury,” the research team concludes.

Reference:
CMAJ 2009;181:E11-E18.