Effects of interferon beta‐1a and ‐1b over time: 6‐year results of an observational head‐to‐head study

Objective –  To evaluate and compare the long‐term efficacy and safety of two different β ‐interferon preparations (IFN‐ β ‐1a vs IFN‐ β ‐1b). Materials and methods –  Two parallel outpatient groups with relapsing–remitting multiple sclerosis (RRMS), according to Poser criteria, were treated with either intramuscular IFN‐ β ‐1a 30  μ g (group A, n  = 62) or subcutaneous IFN‐ β ‐1b 250  μ g (group B, n  = 64). Results –  A statistically significant reduction was seen in the relapse rate ( P  < 0.0001) in both groups. No significant difference was found between the two groups ( P  = 0.43). After 6 years of therapy, the mean Expanded Disability Status Scale score was 3.22 ± 1.47 (Δ 1.03 ± 1.35) in group A and 3.34 ± 1.47 (Δ 0.97 ± 1.47) in group B ( P  = 0.47). Conclusions –  Our study results suggest that the efficacy of IFN‐ β ‐1a 30  μ g once weekly and SC IFN‐ β ‐1b 250  μ g every other day is similar. Both IFN‐ β ‐1a and IFN‐ β ‐1b are effective in slowing disability progression.