Rhabdomyolysis resulting from pharmacologic interaction between erlotinib and simvastatin.

Erlotinib is an epidermal growth factor receptor inhibitor indicated as a second line of therapy for locally advanced and metastatic non–small-cell lung cancer after the failure of 1 previous chemotherpy. Simvastatin belongs to the statin family used to lower blood cholesterol. Drug interaction between erlotinib and statin has not been reported before. Both drugs are major substrates of the CYP3A4 enzyme in the liver. Thus, co-administration of these drugs can increase their serum levels, potentially leading to adverse effects. We report the interaction between erlotinib and simvastatin leading to rhabdomyolysis. Thus, caution is required with increasing usage of both of these drugs.