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.
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.
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
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
Adverse Effects (≥1%)Body as a Whole:
Alopecia, myalgias, flu-like syndrome,
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.
7.89.8 h; Rebif
16 h. Metabolism:
Rapidly inactivated in body fluids and tissue. Half-Life: Avonex
8.610 h; Rebif
Assessment & Drug Effects
- Withhold drug and notify physician if depression or suicidal ideation develops or if there is a worsening of psychiatric
- 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,
- 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.