title: Serum interferon beta-1a (Avonex) levels following intramuscular injection in relapsing-remitting MS patients.
abstract: BACKGROUND
  The pharmacokinetics of IFNbeta-1a in MS patients are poorly understood. We have previously reported an ELISA sensitive and specific for measuring serum IFNbeta-1b levels in patients with MS.
  
  
  OBJECTIVE
  We describe an ELISA to measure interferon beta-1a (Avonex) in the serum of MS patients following IM administration.
  
  
  METHODS
  We have developed an ELISA for detecting serum IFNbeta-1a in MS patients receiving 6 million units (MU) of IFNbeta-1a, IM once weekly. The specificity of this ELISA was confirmed by the lack of cross-reactivity with other cytokines except for IFNbeta-1b.
  
  
  RESULTS
  Serum IFNbeta-1a levels were measured at 3 and 6 months after initiating treatment with IFNbeta-1a in 10 MS patients. At 3 months, all 10 patients had detectable levels ranging from 68 to 86 IU/mL. At 6 months, IFNbeta-1a could be detected in the serum of all but three patients, with levels ranging from 64 to 81 IU/mL. A kinetic study of IFNbeta-1a serum levels in a separate group of six MS patients who had been receiving IFNbeta-1a for several months was carried out. Blood was drawn before and 2, 4, 6, 8, and 24 hours after IFNbeta-1a injection. Peak serum IFNbeta-1a levels were observed at 8 hours and became undetectable at 24 hours after injection.
  
  
  CONCLUSIONS
  The described ELISA may have useful clinical applications in examining the correlation between serum IFNbeta-1a levels and clinical efficacy.
authors.affiliation: Department of Neurology, University of Maryland School of Medicine, Veterans Affairs Medical Center, Baltimore, USA.
authors.forename: O A
authors.initials: OA
authors.lastname: Khan
authors.forename: S S
authors.initials: SS
authors.lastname: Dhib-Jalbut
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007273:Injections, Intramuscular; D016899:Interferon-beta / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D009103:Multiple Sclerosis / Q000097:blood* / Q000628:therapy; D012680:Sensitivity and Specificity
chemical_list: D016899:Interferon-beta