Low Myopathy Rates Associated with Statins as Monotherapy or Combination Therapy with Interacting Drugs in a Group Model Health Maintenance Organization

Study Objective . Because the risk for myopathy increases when 3‐hydroxy‐3‐methylglutaryl coenzyme A inhibitors (statins) are used with other agents known to inhibit cytochrome P450 3A4 in patients with dyslipidemia, we sought to quantify this risk in a diverse, real‐world sample of patients receiving statin therapy. Design . Retrospective chart review. Setting . Kaiser Permanente Colorado (KPCO), a group model health maintenance organization with approximately 360,000 members. Patients . Four hundred sixty‐eight patients who were identified as having a diagnosis of myopathy over a 4‐year period using KPCO computerized data systems. Measurements and Main Results . Medical records were reviewed to confirm myopathy cases associated with statin therapy. Of the 468 patients, 61 had received statin therapy before their diagnosis, and 41 (67%) of these patients had confirmed myopathy (documented creatine kinase level ≥ 1000 IU/L). The prevalence of myopathy was 0.12% with statin mono‐therapy and 0.22% with statins in combination with interacting drugs. Only 17 of the 41 (41%) patients had confirmed myopathy with no other plausible clinical explanation, such as a muscle injury. Increased risk of myopathy associated with statin therapy in combination with interacting drugs approached statistical significance (p=0.052) but was of minimal clinical significance. Conclusion . The prevalence of confirmed myopathy in patients receiving statin therapy is low (< 1%). Combining statin therapy with interacting drugs (e.g., fibrates) was not associated with a clinically important increase in the prevalence of myopathy. The risk of developing myopathy during statin therapy is outweighed by the benefits derived from the therapeutic effects of the therapy.