Avonex, Rebif
Classifications: immunomodulator; interferon;
Therapeutic: immunomodulator
; interferon
Prototype: Interferon alfa-2a
Pregnancy Category: C


Avonex: 33 mcg vial; 30 mcg/5 mL prefilled syringe; Rebif: 22 mcg, 44 mcg vial


Interferon beta-1a is produced by recombinant DNa technology. Interferon beta-1a inhibits expression of pro-inflammatory cytokines including INF-G, thought to be a major factor in triggering the autoimmune reaction that leads to multiple sclerosis. It is believed that INF-G stimulates cytotoxic T-cells and causes degradation by macrophages' enzymes on the myelin sheath of neurons in the spinal cord.

Therapeutic Effect

The mechanisms by which interferon beta-1a exerts its effect on multiple sclerosis is not fully defined; however, time of onset of progression in disability was significantly longer in patients treated with interferon beta-1a.


Relapsing-remitting multiple sclerosis.


Previous hypersensitivity to interferon beta or human albumin, albumin hypersensitivity, hamster protein hypersensitivity; pregnancy (category C) but may cause a spontaneous abortion, lactation.

Cautious Use

Suicidal tendencies, depression, preexisting psychiatric disorders; bone marrow depression; cardiac disease; seizure disorders; thyroid disease; hepatic impairment. Safety and efficacy in children <18 y are not established.

Route & Dosage

Multiple Sclerosis
Adult: IM Avonex 30 mcg qwk SC Rebif 44 mcg 3 times/wk


  • Avonex: Reconstitute single use Avonex vial (33 mcg of lyophilized powder) with 1.1 mL of supplied diluent and swirl gently to dissolve. Withdraw 1.0 mL for administration. Discard any residual drug as the product contains no preservatives.
  • Use within 6 h of reconstitution.
  • Rebif: Give at the same time each day (preferably in the late afternoon or evening) on the same three days of the week at least 48 h apart each week. Dose is usually titrated up from 8.8 mcg to 44 mcg three times a week over a 4-wk period.
  • Inject SC using either a 22 or 44 mcg prefilled syringe. Discard any residual drug as the product contains no preservatives.
  • Store unreconstituted vials or prefilled syringes at 2°–8° C (36°–46° F). May store for ≤30 d at room temperature up to 25° C (77° F). Do not use beyond expiration date.

Adverse Effects (≥1%)

Body as a Whole: Alopecia, myalgias, flu-like syndrome, anaphylaxis. CNS: Headache, fever, fatigue, lethargy, depression, somnolence, weakness, agitation, malaise, confusion or reduced ability to concentrate, anxiety, dementia, emotional lability, depersonalization, suicide attempts, worsening of psychiatric disorders. CV: Tachycardia, CHF (rare). GI: Nausea, vomiting, diarrhea, hepatic injury. Hematologic: Leukopenia, thrombocytopenia, anemia, pancytopenia (rare), thrombocytopenia (rare). Metabolic: Hypocalcemia, elevated serum creatinine, elevated liver transaminases. Skin: Local skin necrosis at injection site, pain at injection site.


Peak: Avonex 7.8–9.8 h; Rebif 16 h. Metabolism: Rapidly inactivated in body fluids and tissue. Half-Life: Avonex 8.6–10 h; Rebif 69 h.

Nursing Implications

Assessment & Drug Effects

  • Withhold drug and notify physician if depression or suicidal ideation develops or if there is a worsening of psychiatric symptoms.
  • Monitor patients with cardiac disease carefully for worsening cardiac function.
  • Lab tests: Monitor periodically liver function tests, renal function tests, routine blood chemistry, and CBC with differential, and platelet count. Monitor thyroid function tests q6mo with preexisting thyroid dysfunction or when clinically indicated.

Patient & Family Education

  • Take a missed dose as soon as possible but not within 48 h of next scheduled dose.
  • Learn about common adverse effects, especially flu-like syndrome (headache, fatigue, fever, rigors, chest pain, back pain, myalgia).
  • Withhold drug and notify physician of depression or suicidal ideation or exacerbation of a preexisting seizure disorder.
  • Note: Women who wish to become pregnant must discontinue therapy.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 09/20/2022 (0)
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