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Interferon alfa-2b Side Effects

Medically reviewed by Last updated on Mar 24, 2024.

Applies to interferon alfa-2b: injection solution. Other dosage forms:


  • Alpha interferons may cause mental health problems or make them worse. Suicide or suicidal thoughts, thoughts of hurting others, depression, forceful actions, hallucinations, and other mood or behavior problems have happened during treatment and within 6 months after the last dose. Relapse of drug addiction has also happened. Alpha interferons may also cause or make infections, blood flow problems, or autoimmune diseases worse. Sometimes, these may be deadly. If you think you have any of these health problems, call your doctor right away. Side effects such as high or low blood pressure, a fast or abnormal heartbeat, chest pain or pressure, trouble breathing, heart attacks, and strokes have happened. Closely read the part in this leaflet which lists when to call your doctor. Many times, but not every time, these side effects get better after stopping this drug.

Serious side effects of Interferon alfa-2b

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

Other side effects of Interferon alfa-2b

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

For Healthcare Professionals

Applies to interferon alfa-2b: injectable kit, injectable powder for injection, injectable solution.


Clinical trials were conducted for various indications using a wide range of doses (from 6 million international units/m2/week in hairy cell leukemia up to 100 million international units/m2/week in melanoma). Most side effects reported during clinical trials were mild to moderate in severity and manageable. Some side effects were transient and most diminished with continued therapy. Influenza-like symptoms (mainly fever, headache, rigors/chills, myalgia, malaise, and fatigue) were reported most often; these side effects were reversible within 72 hours after interrupting or stopping therapy. Side effects were dose-related. In general, more severe toxicities were observed at higher doses; hematologic, hepatic, cardiovascular, and neurologic toxicities were more common with higher doses.

The manufacturer product information for ribavirin should be consulted, if applicable.[Ref]


Very common (10% or more): Fatigue (up to 96%), pyrexia (up to 94%), influenza-like symptoms (up to 79%), asthenia (up to 63%), chills (up to 54%), rigors (up to 42%), chest pain (up to 28%), irritability (up to 22%), unspecified pain (up to 18%), moniliasis (up to 17%), malaise (up to 14%), decreased weight (up to 13%), viral infection

Common (1% to 10%): Facial edema, nonspecific infection, peripheral edema, herpes simplex resistance, thirst, flushing, breast pain

Uncommon (0.1% to 1%): Bacterial infection

Rare (0.01% to 0.1%): Sepsis, resistance mechanism disorders (e.g., altered resistance to infection [rarely life-threatening or fatal]), weakness

Very rare (less than 0.01%): Cachexia, earache, hot flashes/flushes, fungal infection, malignant hyperpyrexia

Frequency not reported: Hernia, edema, hypothermia, nonspecific inflammation, mastitis, increased weight, substernal chest pain, hyperthermia, abscess, Haemophilus, infection, parasitic infection, otitis media, Trichomonas

Postmarketing reports: Asthenic conditions (including asthenia, malaise, fatigue)[Ref]


Very common (10% or more): Decreased granulocyte count (up to 92%), neutropenia (up to 92%), decreased WBC count (up to 68%), decreased hemoglobin (up to 32%), anemia (up to 27%), decreased platelet count (up to 15%), leukopenia

Common (1% to 10%): Thrombocytopenia, bleeding, lymphadenopathy, lymphopenia

Very rare (less than 0.01%): Aplastic anemia, pure red cell aplasia, hemolytic anemia, coagulation disorder, splenomegaly

Frequency not reported: Hypochromic anemia, granulocytopenia, lymphadenitis, lymphocytosis, thrombocytopenia purpura

Postmarketing reports: Pancytopenia (concurrent anemia, leukopenia, thrombocytopenia), idiopathic thrombocytopenia purpura, thrombotic thrombocytopenic purpura[Ref]

Aplastic anemia and pure red cell aplasia have also been reported during postmarketing experience.[Ref]


Very common (10% or more): Myalgia (up to 75%), musculoskeletal pain (up to 21%), arthralgia (up to 19%), back pain (up to 19%)

Common (1% to 10%): Arthritis

Rare (0.01% to 0.1%): Rhabdomyolysis (sometimes serious), myositis, leg cramps

Very rare (less than 0.01%): Arthrosis, bone pain, muscle weakness, myopathy

Frequency not reported: Arthritis aggravated, bone disorder, carpal tunnel syndrome, muscle atrophy, tendinitis, rheumatoid arthritis (new or aggravated), spondylitis, twitching[Ref]

Myositis has also been reported during postmarketing experience.[Ref]


Very common (10% or more): Anorexia (up to 69%), increased alkaline phosphatase (up to 13%)

Common (1% to 10%): Hypocalcemia, dehydration, hyperuricemia

Uncommon (0.1% to 1%): Increased LDH

Rare (0.01% to 0.1%): Diabetes mellitus, hyperglycemia, increased appetite

Very rare (less than 0.01%): Acidosis, aggravation of diabetes mellitus, hypercalcemia, hypertriglyceridemia

Frequency not reported: Alcohol intolerance[Ref]


Very common (10% or more): Nausea (up to 66%), diarrhea (up to 45%), vomiting (up to 32%), dry mouth (up to 28%), abdominal pain (up to 23%), right upper quadrant pain (up to 15%), constipation (up to 14%), gingivitis (up to 14%), stomatitis, dyspepsia

Common (1% to 10%): Loose stools, gastrointestinal (GI) disorder, ulcerative stomatitis, glossitis

Rare (0.01% to 0.1%): Gingival bleeding

Very rare (less than 0.01%): Abdominal distension, colitis, dysphagia, eructation, esophagitis, flatulence, gastric ulcer, GI hemorrhage, GI mucosal discoloration, gum hyperplasia, ileus, increased saliva, ischemic colitis, melena, oral leukoplakia, pancreatitis, rectal bleeding after stool, rectal hemorrhage, tenesmus, tongue disorder, ulcerative colitis

Frequency not reported: Abdominal ascites, gallstones, gastritis, gastroenteritis, halitosis, hemorrhoids, intestinal disorder, mouth ulceration, mucositis, oral hemorrhage, tooth disorder, periodontal disorder (not otherwise specified), dental disorder (not otherwise specified)[Ref]

Pancreatitis has also been reported during postmarketing experience.[Ref]


Very common (10% or more): Elevated AST (up to 63%), elevated ALT (up to 15%)

Common (1% to 10%): Hepatomegaly

Rare (0.01% to 0.1%): Hepatotoxicity (including fatality)

Very rare (less than 0.01%): Abnormal hepatic function tests, bilirubinemia, hepatic encephalopathy, hepatic failure, hepatosplenomegaly, jaundice

Frequency not reported: Biliary pain, hepatitis, increased transaminases (AST/ALT), worsening liver disease[Ref]

Worsening liver disease, including jaundice, hepatic encephalopathy, hepatic failure, and death have been reported after use of this drug in patients with decompensated liver disease, autoimmune hepatitis, or history of autoimmune disease, and in immunosuppressed transplant recipients.[Ref]

Nervous system

Impaired consciousness included cases of encephalopathy.

Frontal subcortical dysfunction and choreic movements of the limbs appeared in a 68-year-old woman almost 2 years after the start of interferon alfa-2b (3 x 10[6] units/day) for chronic myeloid leukemia. She had no history of psychiatric disorders and no hereditary neurodegenerative disease with long-term recombinant interferon therapy. Symptoms of personality changes, short memory loss, and choreic movements progressively worsened over a 4 month period until she became bedridden. One month after this drug was discontinued, patient's cognitive performance had improved and choreic movements had disappeared. Clinical examination of her cognitive performances at six and 12 months later were normal.

Peripheral neuropathy and hearing loss have also been reported during postmarketing experience.[Ref]

Very common (10% or more): Headache (up to 62%), somnolence (up to 33%), dizziness (up to 24%), altered taste/taste perversion (up to 24%), paresthesia (up to 21%), impaired concentration (up to 14%), amnesia (up to 14%)

Common (1% to 10%): Hypoesthesia, vertigo, tremor, migraine, tinnitus

Uncommon (0.1% to 1%): Peripheral neuropathy

Rare (0.01% to 0.1%): Impaired consciousness, neuropathy, polyneuropathy, seizure

Very rare (less than 0.01%): Abnormal coordination, abnormal gait, aphasia, ataxia, central nervous system dysfunction, cerebrovascular hemorrhage, cerebrovascular ischemia, coma, convulsions, deafness, dementia, dystonia, encephalopathy, extrapyramidal disorder, hearing disorder, hearing loss, hyperacusis, hyperesthesia, hyperkinesia, hypertonia, oculomotor nerve paralysis, paralysis, paresis, speech disorder, stupor, syncope, taste loss

Frequency not reported: Bell's palsy, hearing impairment, hypokinesia, hyporeflexia, labyrinthine disorder, loss of consciousness, mononeuropathies, neuralgia, neuritis, parosmia, stroke, frontal subcortical dementia, choreic movements mimicking Huntington's disease[Ref]


Psychosis (including hallucinations) has also been reported during postmarketing experience.[Ref]

Very common (10% or more): Depression (up to 40%), confusion (up to 12%), insomnia (up to 12%), anxiety, emotional lability, nervousness, agitation

Common (1% to 10%): Decreased libido, sleep disorder

Uncommon (0.1% to 1%): Suicidal ideation, suicide attempt, suicide

Rare (0.01% to 0.1%): Aggressive behavior (sometimes directed against others), psychosis (including hallucinations)

Very rare (less than 0.01%): Abnormal thinking, apathy, depression aggravated, feeling of ebriety, neurosis, paroniria, personality disorder

Frequency not reported: Abnormal dreaming, delirium, manic depression, mania, psychosis, mental status change, bipolar disorders

Postmarketing reports: Homicidal ideation[Ref]


Case reports of aseptic necrosis of the skin and ulceration have been described in patients with Kaposi's sarcoma associated with HIV infection treated with this drug.

Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, and urticaria have also been reported during postmarketing experience.[Ref]

Very common (10% or more): Alopecia (up to 38%), rash (up to 25%), increased sweating (up to 21%), pruritus (up to 11%), dry skin

Common (1% to 10%): Dermatitis, purpura, herpes simplex, psoriasis (new or aggravated), maculopapular rash, erythematous rash, eczema, erythema, skin disorder

Very rare (less than 0.01%): Abnormal hair texture, acne, chloasma, dermatitis lichenoides, epidermal necrolysis, erythema multiforme, furunculosis, increased hair growth, melanosis, nail disorders, nonherpetic cold sores, photosensitivity, skin depigmentation, skin discoloration, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria, vitiligo

Frequency not reported: Cellulitis, cold and clammy skin, erythema nodosum, folliculitis, herpes zoster, lipoma, pallor, sebaceous cyst, skin nodule, urticaria, hair discoloration, trichomegaly, radiation recall dermatitis (manifested as erythematous macular rash in region of irradiation), aseptic necrosis of the skin and ulceration, lipoatrophy, cutaneous vasculitides[Ref]


Pulmonary arterial hypertension (PAH) has been reported with alpha interferons, particularly in patients with risk factors for PAH (e.g., portal hypertension, HIV infection, cirrhosis). Such events occurred at various time points normally several months after starting interferon alfa therapy.

Severe asthma developed in 2 patients as soon as 8 weeks after the start of this drug in patients diagnosed with chronic hepatitis C and mild asthma.

Pulmonary fibrosis has also been reported during postmarketing experience.[Ref]

Very common (10% or more): Dyspnea (up to 34%), coughing (up to 31%), pharyngitis (up to 31%), sinusitis (up to 21%), nonproductive cough (up to 14%)

Common (1% to 10%): Nasal congestion, bronchitis, rhinitis, epistaxis, respiratory disorder, rhinorrhea

Rare (0.01% to 0.1%): Pneumonia, pulmonary infiltrates, pneumonitis

Very rare (less than 0.01%): Bronchospasm, hypoxia, laryngitis, pleural pain, pulmonary edema, pulmonary embolism, pulmonary fibrosis, sneezing, stridor, wheezing

Frequency not reported: Asthma, dysphonia, hemoptysis, hypoventilation, pleural effusion, orthopnea, pneumothorax, pulmonary arterial hypertension, rales, respiratory insufficiency, tonsillitis, tracheitis, upper respiratory tract infection, severe asthma

Postmarketing reports: Pulmonary hypertension[Ref]


Very common (10% or more): Injection site inflammation (up to 20%), injection site reaction

Common (1% to 10%): Injection site pain

Rare (0.01% to 0.1%): Injection site disorders

Very rare (less than 0.01%): Injection site necrosis

Frequency not reported: Burning, injection site bleeding, itching[Ref]

Injection site necrosis has also been reported during postmarketing experience.[Ref]


Very common (10% or more): Increased serum urea nitrogen levels (up to 12%)

Common (1% to 10%): Increased serum creatinine

Rare (0.01% to 0.1%): Renal failure, renal insufficiency

Very rare (less than 0.01%): Nephrotic syndrome, nephrosis

Nephrotic syndrome, renal failure, and renal insufficiency have also been reported during postmarketing experience.


Very common (10% or more): Amenorrhea (up to 12%)

Common (1% to 10%): Polyuria, urinary tract infection, micturition frequency, dysmenorrhea, menorrhagia, menstrual disorder, vaginal disorder

Very rare (less than 0.01%): Cystitis, hematuria, impotence, leukorrhea, micturition disorder, nocturia, oliguria, urinary incontinence, uterine bleeding, vaginal hemorrhage

Frequency not reported: Albumin/protein in urine, dysuria, genital pruritus, incontinence, menstrual irregularity, pelvic pain, penis disorder, scrotal/penile edema, sexual dysfunction, vaginal dryness[Ref]


Very common (10% or more): Blurred vision

Common (1% to 10%): Conjunctivitis, abnormal vision, eye pain, lacrimal gland disorder

Rare (0.01% to 0.1%): Retinal hemorrhage, retinopathies (including macular edema), retinal artery or vein obstruction, optic neuritis, papilledema, loss of visual acuity or visual field, cotton wool spots

Very rare (less than 0.01%): Diplopia, dry eyes, night blindness, periorbital edema, photophobia, retinal disorder, serous retinal detachment, stye

Frequency not reported: Lacrimation, nystagmus

Postmarketing reports: Vogt-Koyanagi-Harada syndrome[Ref]

Serous retinal detachment has also been reported during postmarketing experience.[Ref]


Cardiovascular side effects (especially arrhythmia) appeared to be associated with preexisting cardiovascular disease and prior use of cardiotoxic agents.[Ref]

Common (1% to 10%): Hypertension, palpitations, tachycardia

Uncommon (0.1% to 1%): Hypotension

Rare (0.01% to 0.1%): Cardiomyopathy, peripheral ischemia

Very rare (less than 0.01%): Angina pectoris, arrhythmia, atrial fibrillation, bradycardia, cardiac failure, cardiac ischemia, cyanosis, extrasystoles, myocardial infarction, postural hypotension, thrombophlebitis

Frequency not reported: Arteritis, cardiomegaly, coronary artery disorder, cyanosis of the hand, heart valve disorder, hematoma, phlebitis, poor peripheral circulation, polyarteritis nodosa, Raynaud's disease, superficial phlebitis, thrombosis, varicose vein, vasculitis, congestive heart failure, pericardial effusion[Ref]


Common (1% to 10%): Hypothyroidism, hyperthyroidism

Very rare (less than 0.01%): Gynecomastia, virilism

Frequency not reported: Goiter, increased thyroid-stimulating hormone levels

Postmarketing reports: Hypopituitarism[Ref]


Very rare (less than 0.01%): Sarcoidosis, exacerbation of sarcoidosis, increased gamma globulins, transplant rejection

Frequency not reported: Autoimmune disorders, immune-mediated disorders

Postmarketing reports: Systemic lupus erythematosus[Ref]

A broad range of autoimmune and immune-mediated disorders have been reported with alpha interferons including thyroid disorders, systemic lupus erythematosus, rheumatoid arthritis (new or aggravated), idiopathic and thrombotic thrombocytopenic purpura, vasculitis, neuropathies (including mononeuropathies), and Vogt-Koyanagi-Harada syndrome.

Sarcoidosis and exacerbation of sarcoidosis have also been reported during postmarketing experience.[Ref]


Frequency not reported: Allergic reaction

Postmarketing reports: Acute hypersensitivity reactions (including anaphylaxis, angioedema, urticaria, bronchoconstriction)


1. (2001) "Product Information. Intron A (interferon alfa-2b)." Schering Corporation

2. Cerner Multum, Inc. "UK Summary of Product Characteristics."

3. Cerner Multum, Inc. "Australian Product Information."

4. Malik UR, Makower DF, Wadler S (2001) "Interferon-mediated fatigue." Cancer, 92(6 Suppl), p. 1664-8

5. Valles L, Gonzalez M, Polo I, Enguita AB, Vanaclocha F, Ortiz-Romero PL (2009) "Lipoatrophy associated with interferon alfa adjuvant therapy for melanoma." Arch Dermatol, 145, p. 98-9

6. Peck-Radosavljevic M, Wichlas M, Homoncik-Kraml M, et al. (2002) "Rapid suppression of hematopoiesis by standard or pegylated interferon-alpha." Gastroenterology, 123, p. 141-51

7. Kirkwood JM, Bender C, Agarwala S, et al. (2002) "Mechanisms and management of toxicities associated with high-dose interferon alfa-2b therapy." J Clin Oncol, 20, p. 3703-18

8. Moulignier A, Allo S, Zittoun R, Gout O (2002) "Recombinant interferon-alpha-induced chorea and frontal subcortical dementia." Neurology, 58, p. 328-9

9. Bonaccorso S, Marino V, Puzella A, et al. (2002) "Increased Depressive Ratings in Patients With Hepatitis C Receiving Interferon-alpha-Based Immunotherapy Are Related to Interferon-alpha-Induced Changes in the Serotonergic System." J Clin Psychopharmacol, 22, p. 86-90

10. Udina M, Castellvi P, Moreno-Espana J, et al. (2012) "Interferon-induced depression in chronic hepatitis C: a systematic review and meta-analysis." J Clin Psychiatry, 73, p. 1128-38

11. Trautinger F, Knobler RM (1995) "More on interferon-induced cutaneous necrosis." N Engl J Med, 333, p. 1222-3

12. Sheremata WA, Taylor JR, Elgart GW (1995) "More on interferon-induced cutaneous necrosis." N Engl J Med, 333, p. 1223-4

13. Thomas R, Stea B (2002) "Radiation recall dermatitis from high-dose interferon alfa-2b." J Clin Oncol, 20, p. 355-7

14. Wollina U, Graefe T, Fuller J (2002) "Granulomatous slack skin or granulomatous mycosis fungoides -- a case report.Complete response to percutaneous radiation and interferon alpha." J Cancer Res Clin Oncol, 128, p. 50-4

15. Sanders S, Busam K, Tahan SR, Johnson RA, Sachs D (2002) "Granulomatous and suppurative dermatitis at interferon alfa injection sites: Report of 2 cases." J Am Acad Dermatol, 46, p. 611-616

16. Hernandez-Nunez A, Fernandez-Herrera J, Buceta LR, Garcia-Diez A (2002) "Trichomegaly following treatment with interferon alpha-2b." Lancet, 359, p. 1107

17. Bini EJ, Weinshel EH (1999) "Severe exacerbation of asthma: A new side effect of interferon-alpha in patients with asthma and chronic hepatitis C." Mayo Clin Proc, 74, p. 367-70

18. Hejny C, Sternberg P, Lawson DH, Greiner K, Aaberg TM (2001) "Retinopathy associated with high-dose interferon alfa-2b therapy." Am J Ophthalmol, 131, p. 782-7

19. Eland IA, Rasch MC, Sturkenboom MJCM, Bekkering FC, Brouwer JT, Delwaide J, Belaiche J, Houbiers G, Stricker BHC (2000) "Acute pancreatitis attributed to the use of interferon alfa-2b." Gastroenterology, 119, p. 230-3

20. Aleksza M, Lukacs A, Antal-Szalmas P, Hunyadi J, Szegedi A (2002) "Increased frequency of intracellular interleukin (IL)-13 and IL-10, but not IL-4, expressing CD4+ and CD8+ peripheral T cells of patients with atopic dermatitis." Br J Dermatol, 147, p. 1135-41

21. Hamnvik OP, Larsen PR, Marqusee E (2011) "Thyroid dysfunction from antineoplastic agents." J Natl Cancer Inst, 103, p. 1572-87

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.