Myalgia, or common muscle pain, is one of the most common adverse side effects of statin therapy, occurring in about 5% of all patients. The increasing reliance on statins by western society has led to a growing awareness within the medical community of this connection between statins and myalgia, although both the nature of the connection and its prevention are less than clear. Myalgia is most often caused by some sort of trauma, such as over-stretching or over-use of a muscle group or individual muscle. When trauma is not readily identifiable, viral infections may be the cause. For instance, muscle pain is one of the symptoms of influenza.
Since the discovery of mevastatin by a Japanese researcher in the 1970s, the group of medications called statins have been favorably received by the western medical community. These drugs have primarily been used to lower the levels of cholesterol in the human bloodstream, leading to a dramatic reduction in cardiovascular disease. Atorvastatin, the most popular of the statins, is sold under the brand name Lipitor®. Research also indicates that statin therapy may be of use in reducing the incidence of certain types of cancer in some patients. These actual and potential benefits of statin therapy can be seen as outweighing the drawbacks of a potential connection between statins and myalgia.
In a significant subset of cases, it was found that a connection between statins and myalgia was expressed in some statin therapy patients who were deficient in vitamin D, a condition that is virtually endemic in western culture. Correction of the vitamin D deficiency resulted in satisfactory resolution of the myalgia. Vitamin D deficiency, however, does not explain all incidences of myalgia in patients undergoing statin therapy; similarly, there is no connection between statins and myalgia in most patients with the vitamin deficiency.
There is no mechanism by which prescribing doctors can determine which of the many statins will cause myalgia in any particular patient. Likewise, if a patient experiences the disorder, there is no way to tell what the difference will be if the therapy is changed to one of the other statins. Some statins, such as pravastatin and fluvastatin, are more hydrophilic than other statins; that is, they dissolve most readily in water, while other statins are lipophilic, meaning that they dissolve most readily in fats or oils. It has been suggested that it is easier for the lipophilic statins to penetrate cell membranes and cause damage, leading to myalgia, but insufficient research has been performed along these lines.
Exploration of the relationship between statins and myalgia led to the discovery that another of the statins, lovastatin, leads to the expression of a gene thought to promote damage in muscle fibers. The actual incidence of myalgia among lovastatin users, however, doesn’t support the existence of a strong causal relationship.