Note: This document contains side effect information about interferon beta-1a. Some dosage forms listed on this page may not apply to the brand name Avonex.

Summary

Common side effects of Avonex include: flu-like symptoms, fever, headache, myalgia, nausea, and chills. Other side effects include: anemia. Continue reading for a comprehensive list of adverse effects.

Applies to interferon beta-1a: kit, solution.

Serious side effects of Avonex

Along with its needed effects, interferon beta-1a (the active ingredient contained in Avonex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking interferon beta-1a:

More common

• Black, tarry stools
• chest pain
• chills
• cough
• diarrhea
• fever
• flu-like symptoms
• headache
• joint pain
• muscle aches
• nausea
• pain
• painful or difficult urination
• sores, ulcers, or white spots on the lips or in the mouth
• swollen glands
• trouble breathing
• unusual bleeding or bruising
• unusual tiredness or weakness

Less common

• Clumsiness or unsteadiness
• decreased hearing
• difficulty with swallowing
• dizziness
• fainting
• feeling of warmth
• hives or itching
• mood changes, especially with thoughts of suicide
• muscle spasms
• pain or discharge from the vagina
• pelvic discomfort, aching, or heaviness
• redness of the face, neck, arms, and occasionally, upper chest
• redness, swelling, or tenderness at the injection site
• runny or stuffy nose
• seizures
• skin lesions
• sneezing
• sore throat
• speech problems
• stomach pain
• swelling of the face, lips, or eyelids

Rare

• Earache
• general feeling of discomfort or illness
• loss of appetite
• painful blisters on trunk of the body
• painful cold sores or blisters on the lips, nose, eyes, or genitals

Incidence not known

• Bleeding gums
• blue-green to black skin discoloration
• blood in the urine or stools
• bloody nose
• chest discomfort or tightness
• confusion
• constipation
• dark urine
• decreased urine output
• depressed mood
• dilated neck veins
• dry skin and hair
• fast, irregular, or pounding heartbeat
• feeling cold
• general tiredness and weakness
• hair loss
• heavier menstrual periods
• high fever
• irregular breathing
• light-colored stools
• loss of bladder control
• mental depression
• mood or other mental changes
• muscle cramps and stiffness
• nausea or vomiting
• nervousness
• pain, redness, or sloughing of skin at the place of injection
• pale skin
• persistent loss of appetite
• pinpoint red spots on the skin
• puffiness or swelling of the eyelids, or around the eyes, face, lips, or tongue
• redness, blistering, peeling, or loosening of the skin
• sensitivity to heat
• skin rash
• slowed heartbeat
• sudden loss of consciousness
• sweating
• swelling of the face, fingers, feet, or lower legs
• swelling of the mouth or throat
• throat tightness
• upper right stomach pain or tenderness
• weight gain or loss
• yellow eyes and skin

Other side effects of Avonex

Some side effects of interferon beta-1a may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• Heartburn
• indigestion
• sour stomach

Less common

• Hair loss
• trouble sleeping

For Healthcare Professionals

Applies to interferon beta-1a: intramuscular kit, intramuscular powder for injection, subcutaneous kit, subcutaneous solution.

General

Influenza-like symptoms (e.g., myalgia, fever, chills, sweating, asthenia, headache, nausea) are the most common adverse reactions.^[Ref]

Hematologic

Very common (10% or more): Lymphopenia (14%), leukopenia (11%), neutropenia, thrombocytopenia, anemia

Common (1% to 10%): Neutrophil count decreased, hematocrit decreased, blood potassium increased, blood urea nitrogen increased

Uncommon (0.1% to 1%): Platelet count decreased

Rare (Less than 0.1%): Thrombotic microangiopathy including thrombotic thrombocytopenic purpura/hemolytic uremic syndrome,

Frequency not reported: Pancytopenia^[Ref]

Gastrointestinal

Very common (10% or more): Nausea (27%), diarrhea (17%), constipation (12%), vomiting (10%)

Common (1% to 10%): Abdominal pain, toothache

Frequency not reported: Dry mouth, dyspepsia^[Ref]

Dermatologic

Very common (10% or more): Skin rashes (25%), increased sweating

Common (1% to 10%): Contusion, pruritus, erythematous rash, maculopapular rash, night sweats

Uncommon (0.1% to 1%): Alopecia, allergic dermatitis, erythema, urticaria

Rare (0.01% to 0.1%): Skin ulceration/necrosis at the site of injection, Quincke's edema (angioedema), erythema multiforme, Stevens-Johnson syndrome

Very rare (less than 0.01%): Calcified subcutaneous nodules, psoriasis, periungual and nail alterations

Frequency not reported: Rash vesicular^[Ref]

Endocrine

Uncommon (0.1% to 1%): Hypothyroidism, hyperthyroidism^[Ref]

Cardiovascular

Frequency not reported: Cardiomyopathy, congestive heart failure, palpitations, arrhythmia, tachycardia, vasodilatation, chest pain, pulmonary arterial hypertension (PAH) (sometimes reported up to several years after starting treatment)^[Ref]

Genitourinary

Very common (10% or more): Urinary tract infection (19%), cystitis (11%)

Frequency not reported: Metrorrhagia, menorrhagia, urinary incontinence, increase in the frequency of micturition^[Ref]

Hepatic

Very common (10% or more): Alanine aminotransferase increased (26%), aspartate aminotransferase increased (16%)

Common (1% to 10%): Gamma-glutamyl-transferase increased

Uncommon (0.1% to 1%): Hepatitis (with or without icterus)

Rare (Less than 0.1%): Hepatic failure, autoimmune hepatitis

Frequency not reported: Elevation of hepatic transaminases (SGPT and SGOT), bilirubinemia, jaundice^[Ref]

Hypersensitivity

Rare (Less than 0.1%): Anaphylactic reactions

Frequency not reported: Other allergic reactions^[Ref]

Immunologic

Very common (10% or more): Influenza-like symptoms (49%)

Frequency not reported: Systemic lupus erythematosus, anaphylactic reaction, anaphylactic shock, hypersensitivity reactions (angioedema, dyspnea, urticaria, rash, pruritic rash)^[Ref]

Local

Very common (10% or more): Injection site erythema (62%), injection site pain (15%), injection site pruritus (13%), injection site bruising

Common (1% to 10%): Injection site edema, injection site warmth, injection site hematoma, injection site rash

Uncommon (0.1% to 1%): Injection site infections (which could be severe)

Rare (Less than 0.1%): Injection site cellulitis (which could be severe)

Frequency not reported: Injection site abscess, injection site reaction, injection site inflammation, injection site necrosis, injection site bleeding^[Ref]

Musculoskeletal

Very common (10% or more): Myalgia (19%), back pain (20%), pain in extremity (19%), arthralgia (16%), muscular weakness (12%), muscle spasms (10%)

Common (1% to 10%): Muscle spasticity, muscle cramp, neck pain, arthralgia, muscle stiffness, musculoskeletal stiffness

Rare (0.01% to 0.1%): Drug induced lupus erythematosus

Frequency not reported: Arthritis^[Ref]

Nervous system

Very common (10% or more): Headache (67%), dizziness (16%), paresthesia (12%)

Common (1% to 10%): Hypoesthesia

Uncommon (0.1% to 1%): Facial hypoesthesia

Frequency not reported: Neurological symptoms, syncope, hypertonia, seizures, migraine^[Ref]

Metabolic

Frequency not reported: Weight decreased, weight increased^[Ref]

Ocular

Common (1% to 10%): Eye pain

Uncommon (0.1% to 1%): Retinal vascular disorders (i.e. retinopathy, cotton wool spots, obstruction of retinal artery or vein)

Frequency not reported: Eye disorder, abnormal vision, xerophthalmia^[Ref]

Other

Very common (10% or more): Pyrexia (45%), asthenia (24%), pain (23%), fever (20%), chills (19%)

Common (1% to 10%): Fatigue, malaise, hyperthermia, vertigo

Frequency not reported: Tachyphylaxis, sudden hearing loss, tinnitus (ototoxic effects resolved 7 to 14 days after discontinuation of the drug)^[Ref]

Psychiatric

Common (1% to 10%): Depression/suicidal ideation, insomnia, somnolence

Uncommon (0.1% to 1%): Anxiety

Frequency not reported: Suicide attempt, suicide, psychosis, anxiety, confusion, emotional lability, anhedonia, psychotic thoughts, mood disturbances, hypersexuality, aggressive behavior, panic attacks^[Ref]

Respiratory

Very common (10% or more): Oropharyngeal pain (28%), nasopharyngitis (24%), upper respiratory tract infection (21%), cough (16%), sinusitis (14%)

Common (1% to 10%): Rhinorrhea, bronchitis

Rare (0.01% to 0.1%): Dyspnea

Frequency not reported: Pulmonary arterial hypertension^[Ref]

Renal

Rare (Less than 0.1%): Nephrotic syndrome, glomerulosclerosis^[Ref]