Drug interactions are a major consideration in the differential diagnosis of myopathy, as the clinical picture (eg, proximal weakness progressing over a period of months) and laboratory results can be identical to the inflammatory myopathies. Some drugs can also cause electromyographic changes as well as inflammatory changes on muscle biopsy (eg, penicillamine). Statins are associated with myalgias and less frequently with myositis; the risk for these effects increases in a dose-related fashion. Combining statins with other drugs increases the risk for myositis, with the addition of the fibrates conferring the highest risk. Statins used in combination with cyclosporine also carry an increased risk for myositis.1 Concurrent use of niacin or cholestyramine does not increase risk for rhabdomyolysis, but the use of niacin and a statin may increase hepatotoxicity.2
- Lovastatin and gemfibrozil.
1. Asberg A. Interaction between cyclosporine and lipid-
lowering drugs: implications for organ transplant recipients. Drugs 2003;63:367-8.
2. Farmer JA, Gotto AM. Antihyperlipidemic agents. Drug interactions of clinical significance. Drug Safety 1994;11:
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