The number of viral hepatitis infections worldwide is more than 10 times that of acquired immunodeficiency syndrome (AIDS), and more than 1 million people die from viral hepatitis-related diseases each year. However, it is estimated that there are still nearly 30 million patients with chronic hepatitis B (CHB) in China. Interferon (IFN) was approved for CHB treatment in 1992 and pegylated interferon (PegIFN) in 2005. 2010 Chinese guidelines for hepatitis B, as well as the American Association for the Study of Liver Diseases (AASLD), the Asia Pacific Society for the Study of the Liver (APASL), the European Society for the Study of the Liver (EASL) and the National Institute for Health and Clinical Excellence (NICE) The guidelines all recommend IFN/PegIFN for primary care patients. In addition, the reported incidence of hepatitis C in China has been increasing year by year, approaching 16 per 100,000 people in 2012. PegIFN + ribavirin combined with direct antiviral drug regimens can achieve sustained virologic response (SVR) rates of 59%-75% in patients with hepatitis C. Common Adverse Reactions to Interferon Common adverse reactions to IFN (>5%) include injection site inflammation, fatigue, headache, chills, fever, weight loss, dizziness, myalgia, nausea, diarrhea, neutropenia, anemia, and depression. Neutropenia and anemia appeared at the beginning of IFN treatment, flu-like symptoms gradually decreased after 1 week of treatment, and depressive symptoms appeared and gradually increased after 4 weeks of treatment. A retrospective study in China looking at 592 patients with chronic hepatitis C (CHC) who had normal thyroid function prior to IFNα treatment showed that the incidence of abnormal thyroid function (TD) during IFNα treatment was 11.5%, but most were subclinical and only a very small number required continuous drug therapy; women and pre-treatment thyroid peroxidase antibody ( The risk factors for TD are women and positive pre-treatment thyroid peroxidase antibodies (TPOAb). Rare and serious adverse effects Rare and serious adverse effects of IFN () include suicide attempts, major depression, psychosis, aggressive behavior, myocardial infarction, angina pectoris, pericardial effusion, and retinal ischemia. Some of the literature on rare and serious adverse effects of IFN reported abroad is reviewed. Granulocyte deficiency Foreign case report showed that a 19-year-old male patient treated with PegIFNα developed fever, sore throat and general malaise after 6 months, and complete blood count showed complete granulocyte deficiency and undetectable neutrophils in blood smear; after discontinuation of antiviral therapy and administration of empirical broad-spectrum antibiotics and prednisolone, the patient’s neutrophil count completely The neutrophil count returned to normal. Nodular disease is a rare side effect of interferon therapy. Skin involvement may occur alone or in conjunction with systemic involvement; in one third of patients, skin involvement may be the only clinical manifestation. Interferon-induced nodular disease has a benign course; clinical remission can follow discontinuation or dose reduction in most patients, and the decision to reduce or discontinue should be made based on a balance of benefit between treatment and symptom severity. In a patient with human immunodeficiency virus (HIV)/hepatitis C virus (HCV) co-infection, IFNα-2a in combination with ribavirin developed extraocular rectus muscle palsy and no other neurological symptoms after 2 weeks of treatment, which resolved completely after discontinuation without any ophthalmic sequelae. Cases of interferon induced reticular cyanosis, extensive psoriasis, transient vision loss, interstitial pneumonia, acute pancreatitis, renal thrombotic microangiopathy, cerebral leukomalacia, and peripheral neuropathy have also been reported in the literature. Treatment Anemia In anemia due to Peg IFNα in combination with ribavirin therapy, ribavirin may be reduced first by 200 mg or 400 mg and then by another 200 mg if needed; ribavirin needs to be discontinued when hemoglobin levels fall below 85 g/L. In the presence of neutropenia and thrombocytopenia, PegIFN should be reduced when the absolute neutrophil count (ANC) × 109/L and platelets × 109/L; it should be discontinued when ANC × 109/L and platelets 9/L. Hypothyroidism For symptomatic hypothyroidism, most experts recommend continuing Peg IFN and ribavirin on the basis of on-demand replacement therapy; for symptomatic hyperthyroidism, the above drugs should be discontinued and specialist treatment should be received. The incidence of depression in patients treated with the combination of Peg IFNα and ribavirin is 20% to 60%. For mild depression, symptoms should be monitored regularly and antidepressants should be administered, usually without discontinuing PegIFN; moderate depression requires a 50% reduction in PegIFN on top of the above treatment; and severe depression requires discontinuation of PegIFN and ribavirin treatment. Pre-existing symptoms of depression and/or anxiety, depression during prior treatment, ribavirin-induced anemia, long-term treatment, lack of social support, abnormal thyroid function, HIV co-infection, and brain injury can all contribute to the emergence of depression. Patients presenting with depression may be treated with selective 5hydroxytryptamine reuptake inhibitors (SSRI) and 5hydroxytryptamine-norepinephrine reuptake inhibitors (SNRI) such as citalopram, fluoxetine, paroxetine, sertraline, and griseofulvin. If necessary, consult with a neurologist or psychiatrist to guide treatment.