Avonex Side Effects

Generic Name: interferon beta-1a

Please note - some side effects for Avonex may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Avonex - for the Consumer

Avonex

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Avonex:

Flu-like symptoms (eg, headache, tiredness, fever, chills, back pain, muscle aches, weakness); pain, redness, or swelling at the injection site; stomach pain.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); change in vision; chest pain; dark urine; depression; easy bruising or bleeding; extreme tiredness or weakness; fast or irregular heartbeat; feeling cold or hot all the time; increased urination at night; infection at the injection site; seizures; shortness of breath; suicidal thoughts or behaviors; swollen ankles; unexplained change in weight; yellowing of the eyes or skin.

Avonex Prefilled Syringes

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Avonex Prefilled Syringes:

Drowsiness; flu-like symptoms (eg, headache, tiredness, fever, chills, back pain, muscle aches, weakness); pain, redness, or swelling at the injection site; stomach pain.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); change in vision; chest pain; dark urine; depression; easy bruising or bleeding; extreme tiredness or weakness; fast or irregular heartbeat; feeling cold or hot all the time; increased urination at night; infection at the injection site; seizures; shortness of breath; suicidal thoughts or behaviors; swollen ankles; unexplained change in weight; yellowing of the eyes or skin.

Side Effects by Body System

General

In general, the use of interferon beta-1a in patients with multiple sclerosis is limited. It is probable that rarely occurring adverse effects may not have been reported to date. The most commonly reported adverse effects (approximately 60% of patients) have included headaches and a nonspecific flu-like syndrome consisting of muscle aches, fever, chills, and asthenia. These effects appear to diminish with continued treatment. Approximately 4% of patients have discontinued treatment due to adverse effects.

Nervous system

Nervous system side effects have included pain (24%), sleep difficulty (19%), dizziness (15%), muscle spasm (7%), and seizures (1.1%). Migraine has been reported in a placebo-controlled study with Avonex.

In a placebo-controlled study, four patients receiving interferon beta-1a experienced a seizure, while none receiving placebo experienced a seizure. Three of four patients had no prior seizure history. However, a causal relationship with interferon beta-1a has not been confirmed.

Seizures and extrapyramidal symptoms are reported in a 21-year-old man with a history of Tourette's syndrome and Asperger's syndrome, who was recently diagnosed with multiple sclerosis. Generalized tonic-clonic seizures occurred on days 14 and 34 following the start of therapy with interferon beta-1a 30 mcg per week. Given this patient's other neurologic conditions that require a drug regimen with multiple pharmacodynamic properties, it was difficult to establish causality. A new drug regimen without interferon beta-1a has prevented seizure activity and controlled his symptoms of Tourette's syndrome.

Gastrointestinal

Gastrointestinal (GI) side effects have included abdominal pain, dry mouth, and GI upset (i.e., nausea, diarrhea, dyspepsia) in 11% to 33% of patients during placebo controlled studies.

Local

Local side effects have included injection site reactions. Injection-site reactions with interferon beta-1a have been reported rarely, in contrast to interferon beta-1b.

Injection-site reactions were reported more frequently by patients receiving Rebif than in patients receiving Avonex (83% vs. 28%, p less than 0.001) during the EVIDENCE Trial (EVidence of Interferon Dose-response: European North American Comparative Efficacy) where efficacy and safety of interferon beta-1a (Rebif) 44 mcg subcutaneously three times weekly was compared against interferon beta-1a (Avonex) 30 mcg intramuscularly once weekly in patients with relapsing-remitting multiple sclerosis (n=667).

Immunologic

Immunologic side effects have included reports of autoimmune disorders of multiple target organs (idiopathic thrombocytopenia, hyper and hypothyroidism). Serum neutralizing antibodies (NAb) have been detected in 25% of patients treated with Rebif and 2% of patients treated with Avonex. The clinical significance of the presence of NAb to Rebif is unknown. A small preliminary study suggests that switching these patients to alternate interferon beta preparations may not be clinically beneficial. At least one case of subacute cutaneous lupus erythematosus has also been reported, in addition to a case of autoimmune hepatitis.

Subacute cutaneous lupus erythematosus was confirmed in a 43-year-old white man with a long history of multiple sclerosis. He had received interferon beta-1a 3 million intl units weekly for 5 months and listed no family history of autoimmune diseases.

Autoimmune hepatitis in a 38-year-old female treated with interferon beta-1a (Avonex) has been reported to occur after 24 months of treatment.

Neutralizing antibodies developed in 25% receiving Rebif and 2% of patients receiving Avonex during the EVIDENCE Trial (EVidence of Interferon Dose-response: European North American Comparative Efficacy) where efficacy and safety of interferon beta-1a (Rebif) 44 mcg subcutaneously three times weekly was compared against interferon beta-1a (Avonex) 30 mcg intramuscularly once weekly in patients with relapsing-remitting multiple sclerosis (n=667).

Other

Other side effects associated with interferon beta (the specific interferon beta was not identified in the case report) have included sudden hearing loss and tinnitus. Ototoxic effects resolved 7 to 14 days after discontinuation of the drug.

Hepatic

Hepatic side effects have included elevation of hepatic transaminases (SGPT and SGOT), autoimmune hepatitis, bilirubinemia, and jaundice. Severe liver injury, including some cases of hepatic failure requiring liver transplantation, has been reported rarely in patients receiving Rebif. Symptoms of liver dysfunction appeared from one to six months following the initiation of therapy. Hepatic injury, including cases of hepatic failure and elevated serum hepatic enzyme levels, has been reported during postmarketing experience with Avonex.

Fulminant liver failure occurring 7 weeks after the start of Rebif therapy that required a liver transplantation has been reported in a patient who was also receiving nefazodone.

Asymptomatic elevation of hepatic transaminases has been reported, and in some patients has occurred upon rechallenge with Avonex.

Asymptomatic abnormalities of liver enzymes have been reported more frequently in patients receiving Rebif compared with the patients receiving Avonex (18% vs. 9%, p=0.002) during the EVIDENCE Trial (EVidence of Interferon Dose-response: European North American Comparative Efficacy) where efficacy and safety of interferon beta-1a (Rebif) 44 mcg subcutaneously three times weekly was compared against interferon beta-1a (Avonex) 30 mcg intramuscularly once weekly in patients with relapsing-remitting multiple sclerosis (n=667).

Cardiovascular

Cardiovascular side effects have been reported rarely. Congestive heart failure, cardiomyopathy, and cardiomyopathy with congestive heart failure have been reported, during the postmarketing of Avonex, in patients without prior known history to these events. In some cases recurrence was observed upon rechallenge. Vasodilation has also been reported in a placebo-controlled study with Avonex.

Psychiatric

Data from the SPECTRIMS (Secondary Progressive Efficacy Trial of Interferon beta-1a in MS) study suggest that depression is not a side effect of interferon beta-1a.

Psychiatric side effects have included depression, somnolence, suicidal ideation and/or development of new or worsening of preexisting psychiatric disorders, including psychosis.

Hematologic

Hematologic side effects have included leukopenia, lymphadenopathy, thrombocytopenia, and anemia. Other hematologic side effects reported during the postmarketing of Avonex have included decreased peripheral blood counts in all cell lines, including pancytopenia and thrombocytopenia.

Altered leukocyte counts were reported more frequently by patients receiving Rebif than in patients receiving Avonex (11% vs. 5%, p=0.003) during the EVIDENCE Trial (EVidence of Interferon Dose-response: European North American Comparative Efficacy) where efficacy and safety of interferon beta-1a (Rebif) 44 mcg subcutaneously three times weekly was compared against interferon beta-1a (Avonex) 30 mcg intramuscularly once weekly in patients with relapsing-remitting multiple sclerosis (n=667).

Hypersensitivity

Hypersensitivity side effects have included anaphylaxis and other allergic reactions.

Ocular

Ocular side effects have included eye disorder in 4% of patients treated with Avonex. Abnormal vision and xerophthalmia have been reported with Rebif. At least one case of retinopathy has been reported.

Musculoskeletal

Musculoskeletal side effects have included myalgia, back pain, and skeletal pain with the use of Rebif.

Genitourinary

Genitourinary side effects have included urinary incontinence and an increase in the frequency of micturition.

Dermatologic

A 30-year-old woman developed severe widespread urticaria within 30 minutes of her second dose of interferon beta-1a. The patient had suspended therapy with interferon beta-1a due to pregnancy, and reinitiated her treatment 18 months later. Patient underwent prick and intradermal tests with 0.03 mL of the drug diluted in normal saline, starting with a concentration of 1:1000. She had a positive response to the most diluted concentration of the drug.

A 24-year-old female with multiple sclerosis experienced a 12-month history of subcutaneous nodules coincident with Rebif therapy. These lesions became apparent during the early stages of pregnancy at which time she was taking a break from therapy. Prior to pregnancy, she had received 3 years of subcutaneous treatment, requiring injections of Rebif 44 mcg three times weekly. The site of injection had included the thighs, abdomen, upper arms and buttocks, although her preferred site of injection was the abdomen. The examination showed multiple 5 to 10 mm diameter firm, subcutaneous nodules in a band-like distribution across the lower abdomen, below the umbilicus. The subcutaneous nodules stayed palpable after 18 months. No further cutaneous adverse events developed once the site of injection was rotated without preference.

Dermatological side effects have included rare reports of rash (including vesicular rash) during postmarketing experience. At least one case each of severe urticaria, calcified subcutaneous nodules, psoriasis, and periungual and nail alterations have been reported.

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