Multiple Sclerosis Society of Canada

Clemastine Fumarate

  • Also known as: Tavist
  • Route and Dose of Administration: Oral tablet (10.72 mg daily)
  • Type: Remyelination; immunomodulator
  • Emerging Treatment for: Relapsing-Remitting Multiple Sclerosis (RRMS)
  • Status: Completed Phase II Clinical trial
How it Works

Clemastine Fumarate is an oral antihistamine that works by promoting the development of myelin-making cells, called oligodendrocytes. Studies have also shown clemastine’s effects in suppressing the immune system of mice and people without MS. Clemastine is an over the counter allergy medication, however, doses used in the MS clinical trial exceed the daily maximum recommendation.

Research and Results

ReBUILD: Phase II Trial

A phase II single-center, randomized, double-blind, placebo-controlled clinical trial called ReBUILD tested the safety and efficacy of clemastine fumarate in 50 individuals with RRMS. Participants were given oral clemastine fumarate (10.72 mg) daily or a placebo for the first 90 days and for the second 60 days, those that received the treatment were switched to placebo and vice-versa.The primary endpoint measured the speed at which messages were transmitted between the eye and the brain in response to stimulation. Delays in transmission occur when myelin is damaged and reduced delays are an indication of myelin repair. The trial met its primary endpoint which reduced delays by 1.7 milliseconds per eye. The results of the clinical trial were published in the medical journal The Lancet. A larger clinical trial is needed before doctors can recommend this treatment for people with MS.

Adverse Effects Reported

Clemastine Fumarate has not been widely tested in people with MS, so its effects in this population remain largely unknown. The primary adverse effect reported from the ReBUILD clinical trial was fatigue. Other effects reported based on clemastine fumarate’s use as an allergy medication include drowsiness, dizziness, occasional headaches, dry mouth, and nausea.


Green AJ et al. Clemastine fumarate as a remyelinating therapy for multiple sclerosis (ReBUILD): a randomised, controlled, double-blind, crossover trial. Lancet. 2017; 390: 2481-89.

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