Hazardous agent. Cerebrovascular accidents, MI, myocardial ischemia, and/or microangiopathic hemolytic anemia with thrombocytopenia reported (use with caution in cardiovascular disease). Rare, sometimes fatal, pulmonary toxicity (interstitial pneumonia, interstitial lung disease, obliterative bronchiolitis, pulmonary fibrosis). Liver enzyme elevations reported. Hepatic failure and hepatorenal syndrome also reported, particularly in baseline hepatic impairment (use with extreme caution in total bilirubin >3 times ULN). Acute renal failure, renal insufficiency, and hepatorenal syndrome reported (use with caution in patients with or at risk for renal impairment). Use caution with concomitant anticoagulant therapy (elevated INR and bleeding events reported). MI, CVA, and microangiopathic hemolytic anemia with thrombocytopenia noted in patients receiving concomitant erlotinib and gemcitabine. High potential for CYP interactions. Erlotinib levels may be lower in patients who smoke.