interferon beta 1a (Rx)

>10%

Injection site reactions (83% [Rebif]; 28% [Avonex])

Headache (67%)

Flu-like syndrome (61%)

Muscle ache (34%)

Nausea (33%)

URT infection (14%)

Pain (24%)

Fever (23%)

Asthenia (21%)

Diarrhea (16%)

Dizziness (15%)

Infection (11%)

Dyspepsia (11%)

1-10%

Abdominal pain (9%)

Anemia (8%)

Chest pain (6%)

<1%

Aggravation of seizure disorders

Postmarketing Reports

Autoimmune disorders: Drug-induced lupus erythematosus, autoimmune hepatitis

Blood and lymphatic system disorders: Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), hemolytic anemia

Eye disorders: Retinal vascular disorders (ie, retinopathy, cotton wool spots or obstruction of retinal artery or vein)

Skin and subcutaneous tissue disorders: Erythema multiforme, Stevens-Johnson syndrome

Hyperhidrosis

Contraindications

Hypersensitivity to beta interferons, albumin (for albumin-containing formulations)

Cautions

Hepatic impairment, pregnancy, lactation, depression (may cause worsening, suicidal ideation)

Risk of rare but potentially severe hepatic damage

Fllu-like symptoms may occur

Caution in patients with existing cardiovascular disease (angina, heart failure, etc)

Autoimmune disorders (autoimmune hepatitis; idiopathic thrombocytopenia) reported

Efficacy in primary progressive MS not demonstrated conclusively; not recommended

Cases of thrombotic microangiopathy, including thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, some fatal, reported; some cases have been reported several weeks to years after starting interferon beta products; discontinue therapy if clinical symptoms and laboratory findings consistent with TMA occur, and manage as clinically indicated

Pregnancy

Data from a large population-based cohort study, as well as other published studies over several decades, have not identified a drug-associated risk of major birth defects with use during early pregnancy

Findings regarding a potential risk for low birth weight or miscarriage with use of interferon beta products in pregnancy have been inconsistent

Animal data

• In a study in pregnant monkeys, administration of interferon beta during pregnancy resulted in an increased rate of abortion at doses greater than those used clinically

Lactation

Limited published literature has described the presence of interferon beta-1a products in human milk at low levels; there are no data on effects of interferon beta-1a on milk production

Therefore, developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for therapy and any potential adverse effects on breastfed infant from drug or from underlying maternal condition

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Recombinant interferon; antiviral, antiproliferative, immunoregulatory protein; alters response to surface antigen and may enhance immune cell activities

Pharmacokinetics

Onset of action: 12 hr (Avonex)

Duration: 4 days (Avonex)

Peak plasma time: 7.8-9.8 hr (IM); 16 hr (SC)

Concentration: 5.1±1.7 IU/mL (SC)

AUC: 294±81 IU.hr/mL (SC)

Half-Life: 8.6-10 hr (IM); 69±37 hr (SC)

Clearance: 33-55 L/hr (SC)