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interferon [IFN]-beta 1A (Avonex)

Tradename: Avonex. Recombinant protein. Indications: relapsing forms of multiple sclerosis Contraindications: 1) hypersensitivity to albumin 2) hypersensitivity to E. coli-derived products 3) not recommended in patients with liver disease [6] Caution: 1) history of depression 2) history of seizures 3) history of cardiac disease Pregnancy category C Safety in lactation ? Dosage: 6 million units (30 ug) SC/IM weekly Powder for injection: (lyophilized) 33 ug (6.6 million units) Pharmacokinetics: 1) filtered by renal tubules 2) proteolytic degradation during renal tubular reabsorption Monitor: 1) complete blood count (CBC) [6] 2) liver function tests every 6 months [5] - in Canada, baseline, monthly for 1st 6 months, then every 6 months [5] 3) serum chemistries Adverse effects: 1) common (> 10%) a) flu-like symptoms decline after 4-6 weeks of therapy - fever/chills - malaise - myalgias - weakness (asthenia) b) fatigue c) pain & erythema at site of injection 2) less common (1-10%) - tachycardia, syncope, headache, lethargy, depression, emotional lability, anxiety, suicidal ideation, somnolence, agitation, confusion, hypocalcemia, spasticity, nausea/vomiting, anorexia, diarrhea, chronic weight loss, leukopenia, thrombocytopenia, anemia (mild, dose-related), retinal toxicity, visual changes, renal insufficiency (elevated BUN & serum creatinine) elevated liver function tests (mild & transient) 3) uncommon (< 1%) - CHF, alopecia, hepatic failure (autoimmune hepatitis) [3,6] Drug interactions: - decreased clearance/increased toxicity of zidovudine Laboratory: - interferon beta 1a Ab in serum/plasma Mechanism of action: 1) reduces frequency of relapse & new brain lesions visualized by MRI 2) slows progression of physical disability 3) neutralizing antibodies IFN-beta are produced diminishing clinical effectiveness [5]

General

biological response modifier; immune factor; immunomodulator; biomodulator neurologic agent recombinant protein; chimer interferon beta; IFN-beta; fibroblast interferon (IFNB1, IFB, IFNB) pharmaceutical interferon

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  3. U.S. Food and Drug Administration (FDA) http://www.fda.gov/medwatch/SAFETY/2005/safety05.htm#Avonex
  4. Department of Veterans Affairs, VA National Formulary - requires cosign by neurology chief
  5. Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Liver Function Test Scheduling Detail-Document#: 260704 (subscription needed) http://www.prescribersletter.com
  6. Medical Knowledge Self Assessment Program (MKSAP) 17, 18. American College of Physicians, Philadelphia 2015, 2018