Supplementary medication in multiple sclerosis: Real-world experience and potential interference with neurofilament light chain measurement

Background: As vitamins and dietary supplements are obtainable without prescription, treating physicians often ignore their intake by patients with multiple sclerosis (MS) and may therefore miss potential adverse effects and interactions. Objective: We aimed to assess the spectrum and intake frequency of supplementary medication in a cohort of MS patients and to analyse the effect of biotin intake on measurement of serum neurofilament light chain (sNfL), an emerging marker of disease activity. Methods: MS patients visiting our neurology outpatient clinic completed a questionnaire on their past or present use of vitamins or dietary supplements. In addition, the impact of two different doses of biotin (10 and 300 mg/day) on sNfL was studied in healthy volunteers. Results: Of 186 patients, 72.6% reported taking over-the-counter vitamins or dietary supplements currently or previously. Most frequently used was vitamin D (60.0%), followed by biotin. Female patients and patients with primary progressive MS tended to use supplements more frequently. Biotin intake did not interfere with sNfL measurement by single molecule array (Simoa). Conclusions: The use of vitamins and dietary supplements is frequent among patients with MS. Thus, treating physicians should be aware of the pitfalls of supplementary treatment and educate their patients accordingly.