Interferon beta-1b Side Effects

Not all side effects for interferon beta-1b may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to interferon beta-1b: subcutaneous powder for solution

In addition to its needed effects, some unwanted effects may be caused by interferon beta-1b. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking interferon beta-1b:

More common
  • Abdominal or stomach pain
  • break in the skin at the injection site, with blue-black discoloration, swelling, or drainage of fluid
  • flu-like symptoms including chills, fever, generalized feeling of discomfort or illness, increased sweating, and muscle pain
  • headache or migraine
  • hives, itching, or swelling at the injection site
  • irregular or pounding heartbeat
  • redness, pain, or feeling of heat at the injection site
  • stuffy nose
Less common
  • Breast pain
  • bloody or cloudy urine
  • changes in vision
  • cold hands and feet
  • difficult, burning, or painful urination
  • fast or racing heartbeat
  • frequent urge to urinate
  • pain
  • pelvic pain
  • swollen glands
  • troubled breathing
  • unusual weight gain
  • Abnormal growth in the breast
  • benign lumps in the breast
  • bleeding problems
  • bloating or swelling
  • changes in menstrual periods
  • confusion
  • convulsions (seizures)
  • cyst (abnormal growth filled with fluid or semisolid material)
  • decreased sexual ability in males
  • dry, puffy skin
  • feeling cold
  • hyperactivity
  • increased muscle tone
  • increased urge to urinate
  • loss of memory
  • mental depression with thoughts of suicide
  • problems with speaking
  • red, itching, or swollen eyes
  • swelling of the front part of the neck
  • unusual weight loss

Some of the side effects that can occur with interferon beta-1b may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Constipation
  • diarrhea
  • dizziness
  • loss of voice
  • menstrual pain or other changes
  • unusual tiredness or weakness
Less common
  • Anxiety
  • drowsiness
  • hair loss
  • vomiting

For Healthcare Professionals

Applies to interferon beta-1b: subcutaneous powder for injection


The most frequently reported side effects were lymphopenia, injection site reaction, asthenia, flu-like symptoms, myalgia, leukopenia, neutropenia, increased liver enzymes, headache, hypertonia, rash, insomnia, abdominal pain, and pain. The most commonly reported side effects resulting in clinical intervention (e.g., discontinuation of interferon beta-1b, dosage adjustment, or the need for treatment of side effect symptom with concomitant medication) were depression, flu-like symptom complex, injection site reactions, leukopenia, elevated liver enzymes, asthenia, hypertonia, and myasthenia.


Very common (10% or more): Decreased lymphocyte count (less than 1500/mm3; 86%), leukopenia (18%), decreased white blood cell count (less than 3000/mm3; 13%), decreased absolute neutrophil count (less than 1500/mm3; 13%)
Common (1% to 10%): Lymphadenopathy (6%)
Rare (less than 0.1%): Thrombotic microangiopathy (at least 1 patient)
Postmarketing reports: Anemia, thrombocytopenia


"Injection site reaction" includes all side effects occurring at the injection site (except injection site necrosis), which include injection site inflammation, injection site pain, injection site hypersensitivity, injection site mass, injection site edema, injection site reaction, injection site hemorrhage, and injection site atrophy.

About 69% of patients experienced injection site reactions during the first 3 months of therapy with the incidence decreasing to about 40% at the end of the trials.

Injection site necrosis generally occurred within the first 4 months of therapy, but has been reported over 1 year after start of therapy during postmarketing experience. The necrotic lesions usually had a diameter of 3 cm or less, but larger areas have been observed. The necrosis typically extended to subcutaneous fat only, but has extended to fascia overlying muscle. In some lesions where biopsy results were available, vasculitis has been observed.

Very common (10% or more): Injection site reaction (78%), injection site inflammation (42%), injection site pain (16%)
Common (1% to 10%): Injection site necrosis (4%), injection site hypersensitivity (4%), injection site mass (2%), injection site edema (2%)
Frequency not reported: Injection site hemorrhage, injection site atrophy, nonspecific reactions, severe necrotic lesions, injection site vasculitis


Very common (10% or more): Flu-like symptom complex (denotes flu syndrome and/or a combination of at least 2 side effects from fever, chills, myalgia, malaise, sweating; 57%), asthenia (53%), pain (42%), fever (31%), chills (21%), peripheral edema (12%)
Common (1% to 10%): Chest pain (9%), malaise (6%)
Postmarketing reports: Fatal capillary leak syndrome

The incidence of flu-like symptom complex decreased to 10% at the end of clinical trials. The median duration was 7.5 days in one study.

Development of fatal capillary leak syndrome has been associated with the administration of cytokines to patients with a preexisting monoclonal gammopathy.


Frequency not reported: Depression, suicidal ideation, suicide attempts, suicide, nervousness
Postmarketing reports: Anxiety, confusion, emotional lability, psychotic symptoms

During clinical studies, 3 suicides and 8 suicide attempts were reported among 1532 patients treated with interferon beta-1b compared to 1 suicide and 4 suicide attempts among 965 patients on placebo.

Nervous system

Seizures have been temporally associated with beta interferons in clinical trials and during postmarketing experience. It is not known if such events were due to primary seizure disorder, effects of multiple sclerosis alone, use of beta interferons, other possible precipitants of seizures (e.g., fever), or to some combination of these.

Sudden hearing loss, which was reversible within 7 to 14 days of drug discontinuation, has been reported.

Very common (10% or more): Headache (50%), insomnia (21%), incoordination (17%)
Frequency not reported: Somnolence, seizures, sudden reversible hearing loss
Postmarketing reports: Convulsion, dizziness


Very common (10% or more): Hypertonia (40%), myalgia (23%)
Frequency not reported: Increase in spasticity, leg cramps, myasthenia
Postmarketing reports: Arthralgia

In a study of 124 multiple sclerosis patients, myalgia and myasthenia were reported in 44% and 13% of the patients, respectively.

A study of 19 patients with primary progressive multiple sclerosis reported frequent and clinically significant increase in spasticity that appeared approximately 2 months after start of interferon beta-1b.


A case of sarcoid-like dermatitis was reported in a 57-year-old white man diagnosed with multiple sclerosis. The cutaneous eruption that developed 2 months after initiation of interferon beta-1b therapy histologically resembled sarcoidal granulomas, but without distinctive features of true sarcoidosis.

A case of cutaneous necrosis in a 38-year-old woman diagnosed with relapsing-remitting multiple sclerosis was believed to be a result of an immunological response to the improperly dissolved lyophilized drug. The patient was rechallenged with the drug, after introducing changes to the way she reconstituted the drug, without any reports of scars.

Very common (10% or more): Rash (21%)
Common (1% to 10%): Skin disorder (10%)
Frequency not reported: Contact dermatitis, erythema nodosum, exfoliative dermatitis, furunculosis, hirsutism, leukoderma, lichenoid dermatitis, maculopapular rash, psoriasis, seborrhea, benign skin neoplasm, skin carcinoma, skin hypertrophy, skin necrosis, skin ulcer, vesiculobullous lesions, sarcoid-like dermatitis, septal panniculitis
Postmarketing reports: Alopecia, pruritus, skin discoloration, urticaria


Very common (10% or more): Abdominal pain (16%)
Frequency not reported: Constipation, dyspepsia
Postmarketing reports: Diarrhea, nausea, pancreatitis, vomiting


Very common (10% or more): Elevated alanine aminotransferase (SGPT greater than 5 times baseline; 12%)
Common (1% to 10%): Elevated aspartate aminotransferase (SGOT greater than 5 times baseline; 4%), asymptomatic elevation of serum transaminases
Rare (less than 0.1%): Severe hepatic injury (including cases of hepatic failure [some due to autoimmune hepatitis])
Frequency not reported: Elevated liver enzymes
Postmarketing reports: Hepatitis, elevated gamma-glutamyltransferase

During clinical trials, elevations of SGPT and SGOT to greater than 5 times baseline levels led to dose reduction or treatment discontinuation in some patients.


A 19-year-old white woman diagnosed with multiple sclerosis experienced severe vaginal bleeding when her dose of interferon beta-1b was increased, 1 month from the start of therapy, from 4 to 8 million international units.

Very common (10% or more): Urinary urgency (11%)
Common (1% to 10%): Metrorrhagia (9%), impotence (8%)
Frequency not reported: Menstrual disorders/irregularities, severe vaginal bleeding, dysmenorrhea, prostatic disorder, urinary frequency
Postmarketing reports: Menorrhagia


Common (1% to 10%): Hypertension (6%)
Frequency not reported: Peripheral vascular disorder, congestive heart failure (CHF), cardiomyopathy with CHF, worsening of CHF
Postmarketing reports: Cardiomyopathy, palpitations, tachycardia, vasodilatation

CHF, cardiomyopathy, and cardiomyopathy with CHF have been reported in patients without known predisposition to such events, and without establishment of other known etiologies. In some cases, these events were temporally related to interferon beta-1b. Recurrence upon rechallenge was observed in some patients.


Rare (less than 0.1%): Anaphylaxis/anaphylactic reactions
Frequency not reported: Other allergic reactions (including dyspnea, bronchospasm, tongue edema, skin rash, urticaria)


Common (1% to 10%): Dyspnea (6%)
Postmarketing reports: Bronchospasm


Postmarketing reports: Increased triglycerides, anorexia, decreased weight, increased weight


The development of antibodies against interferon beta has been reported, often as early as 3 months after the start of treatment. The antibodies may bind to and block the beneficial effect of interferon beta in multiple sclerosis. The overall clinical significance is unknown.

Neutralizing antibodies formation occurred after the 24-week treatment in 95% of patients treated with natural interferon beta compared to 27% of patients treated with recombinant interferon beta.

Results of a prospective study suggest that several autoimmune events may occur during interferon beta treatment of multiple sclerosis and recommends the close monitoring of thyroid, liver function, and autoantibodies.

Frequency not reported: Development of antibodies against interferon beta


Postmarketing reports: Hypothyroidism, hyperthyroidism, thyroid dysfunction


Rare (less than 0.1%): Subacute renal failure due to thrombotic microangiopathy (at least 1 patient)
Postmarketing reports: Hemolytic uremic syndrome, nephrotic syndrome with minimal histologic changes of the glomerulus

Hemolytic uremic syndrome and nephrotic syndrome with minimal histologic changes of the glomerulus have been reported during postmarketing experience. Upon withdrawal of interferon beta therapy these side effects subsided.

A 53-year-old female with multiple sclerosis developed subacute renal failure due to thrombotic microangiopathy following 8 years of therapy with interferon beta-1b.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.