Beta-interferons are used as first-line therapy for relapsing-remitting multiple sclerosis in Brazil. In order to evaluate the possible inferiority of one of the beta-interferons available and support a guideline update, we conducted an eleven-year (January 2000 to December 2010) nationwide real-world performance assessment using the Unified Health System (SUS) databases.

We assessed whether patients using subcutaneous beta-interferon switched treatment, relapsed or died (composite event) earlier than patients using intramuscular beta-interferons. Patients without a dispensing registry longer than three months were censored. We used the Kaplan-Meier method to estimate the cumulative probability of persistence on initial treatment, and compared groups with the Log-rank test. The influence of the drug on the occurrence of event was assessed with Cox proportional hazards analysis.

The number of patients included was 12,154, and the majority started treatment with subcutaneous beta-interferon-1a (45.7 percent), followed by subcutaneous beta-interferon-1b (27.7 percent) and by intramuscular beta-interferon (26.6 percent). Women represented 73.1 percent and the mean age was 38.93±11.34 years old. The group of patients who used intramuscular beta-interferon switched treatment, relapsed or died earlier (median 47 months; 95 percent Confidence Interval, CI 44–52) than patients using the subcutaneous beta-interferons, (69 months (95 percent CI 64–76) for beta- interferon 1a and 73 (95 percent CI 66–84) months for beta-interferon 1b) (p< .0001 for both comparisons). Accordingly, the use of intramuscular beta-interferon was associated with a higher probability of event (Hazard ratio, HR 1.38; 95 percent CI 1.29-1.48), while the use of the other beta-interferons had a protective effect (1a: HR .86; 95 percent CI .81-.92; 1b: HR .89; 95 percent CI .83-.95).

The inferiority of intramuscular beta-interferon found in the real-world corroborates findings from head-to-head studies and systematic reviews conducted by Cochrane and the National Commission for Technology Incorporation in SUS (CONITEC/Brazil). This result led to disinvestment in intramuscular beta-interferon and was the first case of clinical guideline update using real-world evidence in Brazil.