Interferon Beta

Allergic reactions, including anaphylaxis, have been reported. Some reactions may occur after prolonged use. Discontinue therapy if anaphylaxis or other allergic reactions occur.

Autoimmune disorders including idiopathic thrombocytopenia, hyper- and hypothyroidism and rarely autoimmune hepatitis have been reported. Consider discontinuation of treatment if patient develops a new autoimmune disorder.

Pancytopenia (rare), leukopenia, and thrombocytopenia have been reported. Monitor blood counts at 1, 3, and 6 months post therapy initiation and periodically thereafter. Events may recur with rechallenge.

Associated with a high incidence of flu-like adverse effects; use of analgesics and/or antipyretics on treatment days may be helpful.

Rare cases of severe hepatic injury, including cases of hepatic failure requiring transplantation, have been reported in patients receiving interferon beta-1a; risk may be increased by ethanol use or concurrent therapy with hepatotoxic drugs. Some reports indicate symptoms began after 1 to 6 months of treatment. Transaminase elevations may be asymptomatic. Use with caution in patients with active or a history of liver disease, alcohol abuse, or increased serum ALT (>2.5 times ULN) at baseline. Obtain liver function tests at 1, 3, and 6 months post therapy initiation and periodically thereafter. Treatment should be suspended immediately if jaundice or symptoms of hepatic dysfunction occur. Consider dose reductions or temporary discontinuation if ALT >5 times ULN.

Severe injection site reactions have occurred, including pain, erythema, edema, cellulitis, abscess, and necrosis. Necrosis may occur at single and multiple sites. Some reactions have occurred ≥2 years after initiation; reactions typically resolve with conservative treatment (antibiotics or surgical intervention may be required). Patient and/or caregiver competency in injection technique should be confirmed and periodically re-evaluated.

Interferons have been associated with psychiatric adverse events (psychosis, depression, suicidal behavior/ideation) in patients with and without previous psychiatric symptoms; use with caution in patients with depression. Patients exhibiting symptoms of depression or other severe psychiatric symptoms should be closely monitored and discontinuation of therapy should be considered.

Cases of thrombotic microangiopathy manifesting as thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome (HUS) (some fatal) have been reported (Hunt 2014; Mahe 2013; Rebif Canadian product labeling 2016). Some cases may occur after several years of therapy. Monitor for new onset hypertension, thrombocytopenia, or impaired renal function; discontinuation of therapy and prompt treatment may be necessary if TTP/HUS are confirmed. Disease-related concerns:

Use with caution in patients with preexisting cardiovascular disease. Rare cases of new-onset cardiomyopathy and/or HF have been reported. In a scientific statement from the American Heart Association, interferon has been determined to be an agent that may either cause reversible direct myocardial toxicity or exacerbate underlying myocardial dysfunction (magnitude: moderate/major) (AHA [Page 2016]).

Use with caution in patients with hepatic impairment or in those who abuse alcohol.

Use with caution in patients with a history of seizure disorder.

Thyroid abnormalities may develop with use; may worsen pre-existing thyroid conditions. Monitor thyroid function tests every 6 months or as clinically necessary. Special populations:

Safety and efficacy have not been established for this use. Dosage form specific issues:

Some formulations contain albumin, which may carry a remote risk of transmitting Creutzfeldt-Jakob or other viral diseases. Interferon beta-1a formulations that contain albumin are contraindicated in albumin-sensitive patients.

The packaging (prefilled syringe tip cap) may contain latex.