The main purpose of this study is to assess clemastine as a remyelinating agent in patients with relapsing forms of multiple sclerosis. The study will also evaluate the tolerability of clemastine, originally approved as first-generation antihistamine, in patients with multiple sclerosis. Study procedures will include assessments for evidence of remyelination in the anterior visual pathway and in the brain using electrophysiologic techniques and magnetic resonance imaging. The study will also assess the robustness and stability of this clinical effect in patients taking clemastine for up to 3 months. Patients in this study can remain on their standard disease modifying treatment during the course of the study. However, patients cannot participate in any other investigational new drug research study concurrently.