Objective: To evaluate the cost effectiveness of subcutaneous interferon-beta-1a (IFNbeta-1a) 44mug three times weekly in relapsing-remitting multiple sclerosis (RRMS) using an econometric model.

Methods: Data on RRMS patients treated with IFNbeta-1a 22 or 44mug subcutaneously three times weekly or placebo for up to 4 years were obtained from the Prevention of Relapses and disability by Interferon-beta-1a Subcutaneously in Multiple Sclerosis (PRISMS) study. The area under the Expanded Disability Status Scale (EDSS) score-time curve was used as a measure of disability and the effectiveness of therapy was expressed as EDSS-months of disability prevented. Costs were calculated for the UK and France, and results were projected to 10 and 20 years using a time series regression model.

Results: Over 10 years, treatment with IFNbeta-1a 44mug subcutaneously three times weekly prevented 121 EDSS-months of additional disability at a cost of Euros (euro)732 each (year of costing 2000). Over 20 years, 321 EDSS-months were saved at a cost of euro359 per month (year of costing 2000).

Conclusions: This analysis indicated that IFNbeta-1a 44mug subcutaneously three times weekly is cost effective in RRMS and that treatment becomes increasingly cost effective over time.