Hazardous agent. May cause myelosuppression (including neutropenia, thrombocytopenia, lymphopenia, aplastic anemia). CNS effects (dizziness, confusion, somnolence, or fatigue) might occur. Serious cutaneous reactions, including vesiculobullous eruptions, Stevens-Johnson syndrome, and exfoliative dermatitis, reported (rarely) with use, with or without ribavirin therapy. Commonly associated with flu-like symptoms, including fever. Gastrointestinal hemorrhage, ulcerative and hemorrhagic/ischemic colitis observed with interferon alpha treatment. Hepatic decompensation and death associated with use of alpha-interferons, in cirrhotic chronic hepatitis C. Severe acute hypersensitivity reactions occurred rarely. Serious and severe infections (bacterial, viral, and fungal) reported. Severe psychiatric adverse effects (including depression, suicidal ideation, and suicide attempt) may occur (avoid use in severe psychiatric disorders, and use with extreme caution in history of depression). Ocular effects, including retinal hemorrhages, cotton wool spots, and retinal artery or vein obstruction, can occur. Pancreatitis might develop. Pulmonary effects (dyspnea, pulmonary infiltrates, pneumonia, bronchiolitis obliterans, interstitial pneumonia, and sarcoidosis, resulting in potentially fatal respiratory failure) may occur (use with caution in pulmonary dysfunction or history of pulmonary disease). Use with caution in increased risk for severe anemia (e.g. spherocytosis, history of GI bleeding), in autoimmune disease, in prior cardiovascular disease, and in diabetes mellitus (hyper-/hypoglycemia reported). In hepatitis B, flares (transient and potentially severe increases in serum ALT) may occur. Infectious disorders, or ischemic disorders might occur. Use with caution in renal dysfunction (CrCl <50 mL/minute), and in pre-existing thyroid disease. Combination treatment with ribavirin may cause birth defects and/or fetal mortality, hemolytic anemia (may worsen cardiac disease), genotoxicity, mutagenicity, and may possibly be carcinogenic. Use with caution in the elderly.