A Study of Oxidative Pathways in MS Fatigue

This is a 4-week randomized, placebo-controlled, parallel group, double-blind, single center trial on effect of N-acetyl cysteine versus placebo on fatigue in patients with progressive MS defined by McDonald criteria. Subjects who enter the treatment phase of study, will be randomly assigned to either N-acetyl cysteine (1250 mg three times a day) or placebo (three times a day) for 4 weeks. There will be 3 in-person study visits (screening, baseline, and week 4) and 2 visits over the phone (week 2, and week 6 which is 2 weeks after completing last study drug dose). Visits will all occur in the morning to maximize consistency of assessments and evaluate main outcomes within 2 hours of morning dose of study medication. Fatigue questionnaires, and research samples will be obtained before neurological examination, or magnetic resonance imaging. Research blood draws will be obtained just after fatigue questionnaire completion. Brain spectroscopy will be obtained less than 2 hours after morning dose of study drug to maximize detection of the biological effect of study medication.