Transfer of Interferon β-1a into Human Breastmilk

Aim: This study determined the transfer of intramuscular interferon beta-1a into human milk and provides an estimate of infant exposure to this antiviral in six women chronically receiving intramuscular interferon beta-1a (Avonex (R), Biogen Idec, Research Triangle Park, NC). Methods: Interferon beta-1a was measured at various times at steady state in milk samples collected from women receiving interferon beta-1a at 30 mu g/week. Results: Average milk concentrations were 46.7, 97.4, 66.4, 77.5, 103.1, 108.3, 124, and 87.9 pg/mL at 0, 1, 4, 8, 12, 24, 48, and 72 hours, respectively, after dosing. Using the highest value measured (179 pg/mL), the estimated relative infant dose would be 0.006% of the maternal dose. Conclusions: These data clearly suggest that interferon beta-1a does not penetrate the milk compartment significantly and that levels in milk are far subclinical. No side effects were noted in any of the breastfed infants.