Long-Term Adherence to Interferon β Therapy in Relapsing-Remitting Multiple Sclerosis

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Abstract
To assess the proportion and the reasons of drop-outs in relapsing-remitting multiple sclerosis patients treated with interferon-beta (IFNB) and the outcome of switching subjects. Patients stopping IFNB were classified according to the reason of drop-out: perceived lack of efficacy (PLE) side effects (SE) and other reasons. Long-term adherence was described using the Kaplan-Meier curves. We evaluated 225 subjects (158 women; age = 36.6 +/- 9.2 years, disease duration = 8.0 +/- 6.1 years, Expanded Disability Status Scale score = 1.9 +/- 1.2) who received Betaferon (46), Avonex (88) and Rebif (91) therapy. The mean follow-up duration was 4.2 +/- 2.7 years. Forty-six percent of patients suspended therapy, 29% because of PLE, 15% because of SE and the remaining 2% due to other reasons. Twenty-five out of 33 subjects who suspended IFNB because of SE and 62 out of 65 patients who suspended the therapy due to PLE were switched to another disease-modifying drug. At the end of the follow-up, the majority of these patients could continue the treatment. When starting IFNB therapy in relapsing-remitting multiple sclerosis, a relatively high proportion of discontinuation is to be expected over time. Switching from a treatment to another taking into account the reasons of drop-out and the disease activity is a suitable option.