Muscle Abnormalities in Four Patients Taking Statins To Treat Unfavorable Cholesterol Levels

Summaries for Patients are a service provided by Annals to help patients better understand the complicated and often mystifying language of modern medicine.

Summaries for Patients are presented for informational purposes only. These summaries are not a substitute for advice from your own medical provider. If you have questions about this material, or need medical advice about your own health or situation, please contact your physician. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the American College of Physicians-American Society of Internal Medicine.

The summary below is from the full report titled "Statin-Associated Myopathy with Normal Creatine Kinase Levels." It is in the 1 October 2002 issue of Annals of Internal Medicine (volume 137, pages 581-585). The authors are PS Phillips, RH Haas, S Bannykh, S Hathaway, NL Gray, BJ Kimura, GD Vladutiu, JDF England, and the Scripps Mercy Clinical Research Center.

What is the problem and what is known about it so far?

Statins, also known as HMG coenzyme A reductase inhibitors, are medications commonly used to treat high cholesterol levels. Statins are very effective in getting cholesterol levels into the desired range, and they have had few side effects. However, statins do cause a muscle condition called myopathy. In fact, one statin (cerivastatin) was taken off the market because patients frequently developed myopathy while taking it. Patients with myopathy have muscle tenderness and weakness. Measuring blood levels of the muscle protein called creatine kinase helps doctors to diagnose myopathy because in patients with muscle damage, the protein leaks out of muscle cells and into the blood. Some patients receiving statins develop muscle pain and weakness but have normal serum creatine kinase levels. Doctors have been wondering whether these symptoms represent milder forms of muscle damage related to statins.

Why did the researchers do this particular study?

The researchers report four cases of myopathy associated with statins in patients with normal creatine kinase levels.

Who was studied?

While doing a larger study of muscle symptoms in patients taking statins, the researchers found four patients with muscle pain and weakness during statin therapy that went away when the patients stopped taking the statins. All four patients had normal creatine kinase levels.

How was the study done?

As part of the larger study, the researchers gave the patients statin or placebo and asked the patients to guess which they were taking. The placebo was a pill that looked, smelled, and tasted like statin but contained no active ingredient. All patients had strength testing. In three of the four patients, the doctors took samples of muscle to examine under a microscope (muscle biopsy) both during and after statin therapy.

What did the researchers find?

The patients could correctly guess when they were taking statins because they developed muscle pain and weakness during that therapy. Strength testing showed muscle weakness when the patients were taking statins and normal strength when they were not taking statins. Muscle biopsy samples obtained when patients were taking statins showed changes of myopathy. These changes were not present on the samples taken after the patients stopped statins.

What were the limitations of the study?

This study does not tell us anything about how frequently statin-associated myopathy with normal creatine kinase levels occurs.

What are the implications of the study?

When patients taking statins develop muscle pain and weakness, they may have muscle damage even if blood test results are normal. More research is necessary to learn how frequently patients taking statins develop myopathy with normal creatine kinase levels.