Hematologic toxicity, including neutropenia and severe thrombocytopenia may occur (risk is increased if pre-treatment platelet counts <75000/μL). May cause hypotension (caution with dehydration, history of syncope, or medications associated with hypotension), development or exacerbation of congestive heart failure and decreased left ventricular ejection fraction (caution in risk factors or existing heart disease), and QTc prolongation. Acute liver failure reported (rarely) in patients receiving multiple concomitant medications. Because bortezomib is metabolized by cytochrome P-450 microsomal enzymes, clearance of the drug may be reduced in hepatic impairment. Asymptomatic increases in serum hepatic aminotransferase concentrations, hyperbilirubinemia, and hepatitis reported. Herpes zoster and herpes simplex reactivation reported. May cause peripheral neuropathy (usually sensory but may be mixed sensorimotor). Reversible posterior leukoencephalopathy syndrome reported (rarely). Pulmonary disorders including pneumonitis, interstitial pneumonia, lung infiltrates, and acute respiratory distress syndrome reported. Pulmonary hypertension (without left heart failure or significant pulmonary disease) reported rarely. May cause tumor lysis syndrome (risk is increased in patients with high tumor burden prior to treatment). Hyper- and hypoglycemia may occur in diabetic patients receiving oral hypoglycemics. Risk of serious adverse events.