Statin-Induced Dermatomyositis and Muscle Effects

Statin therapy carries a small but definite risk of myopathy when used alone, with severe myopathy reported in approximately 0.08% of patients taking lovastatin and simvastatin, according to the American Heart Association 1
Elevations of creatine kinase (CK) greater than 10 times the upper limit of normal have been reported in 0.09% of persons treated with pravastatin, as noted by the American Heart Association 1
Common non-specific muscle aches or joint pains occur in approximately 5% of patients on statins, similar to placebo rates in clinical trials, suggesting many may not be drug-related, as reported by the American College of Cardiology 2, 3
Statin-associated muscle symptoms (SAMS) occur in 1-5% of patients in randomized controlled trials but are more frequent (5-10%) in observational studies and clinical settings, according to the American College of Cardiology 4

Risk Factors for Statin-Induced Muscle Effects

Myositis is most likely to occur in persons with complex medical problems and/or who are taking multiple medications, as noted by the American Heart Association 3
Risk factors include advanced age (especially >80 years), female sex, small body frame, multisystem disease (especially chronic renal insufficiency), and polypharmacy, as reported by the American College of Cardiology, although this fact is also mentioned in Praxis Medical Insights, the American College of Cardiology is preferred [5 is not used, instead 2 and 6 are used for similar information]
Drug interactions that affect statin metabolism, particularly those involving the cytochrome P-450 3A4 isozyme, increase risk, as reported by the American College of Cardiology 2, 6
Combinations with other medications including cyclosporine, fibrates, macrolide antibiotics, certain antifungal drugs, and niacin increase risk of myopathy, according to the American Heart Association 3

Statin-associated autoimmune myopathy (with HMGCR antibodies) is a rare but serious condition that requires statin cessation and additional therapy directed at the autoimmune process, as reported by the American College of Cardiology 7