Myopathy during treatment with the antianginal drug ranolazine.

Ranolazine is a medication indicated for treatment of chronic angina and is a partial inhibitor of the fatty acid β-oxidation. We present an adult patient who developed subacute progressive muscle weakness and exercise-induced myalgia, soon after increasing the daily dose of ranolazine, in the setting of therapy with simvastatin. CK persisted normal throughout the duration of the weakness and muscle biopsy showed a lipid storage myopathy for which no underlying genetic defect was identified. Discontinuation of both drugs resulted in clinical improvement. Although simvastatin may have contributed to the myopathy, the temporal relation between the increase in ranolazine dose and the onset of the weakness would favor ranolazine as major culprit for the weakness.