Patient description: The patient is a 20 year old Caucasian female presents to the clinic with one-sided vision lost and facial weakness, dysarthria and numbness lasting for 1 day. She visited her PCP and underwent brain MRI which revealed a single plaque in the brainstem. After few months, she experienced lower extremities weakness led to balance problem. The second MRI revealed another lesion in the left cerebral hemisphere. The diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) is confirmed after the second MRI. Her past surgical history is significant for a C-section 2 years ago and she has a one child. She is divorced and is not currently in any sexual relationship. She smokes 10 cigarettes per day and drinks alcohol occasionally. She is working as an editor in a publisher company and she is happy that she can keep working from home most of the time. She is under the treatment of RRMS from 7 months ago.

Clinical trial eligibility criteria: eligible ages (years): 18.0-60.0,  Multiple Sclerosis, Relapsing-Remitting Participants must be between age 18 and 60 years Sexually active men and women of child-bearing potential, defined as those who are not postmenopausal (24 consecutive months) or permanently sterilised, must agree to use adequate contraception. Adequate contraception is defined as methods of birth control which result in a low failure rate [i.e. less than 1% per year] when used consistently and correctly such as implants, injectables, combined oral contraceptives, some intrauterine devices (IUDs), barrier contraceptives, sexual abstinence or vasectomised partner. Adequate contraception is required during domperidone treatment and for one month after stopping treatment Participants must have MS defined according to the McDonald (Polman et al. 2011) Participants must have RRMS according to Lublin et al. (2014) Participants must have been treated with a stable approved dose of glatiramer acetate, interferon-beta, fingolimod, dimethyl fumarate, or teriflunomide for at least 6 months Participants must be scheduled to have a clinically indicated brain MRI to monitor DMT effectiveness Participants must have at least one gadolinium enhancing lesion on their DMT monitoring MRI (screening MRI) Participants must report at least 80% adherence to their current DMT and have had no treatment discontinuation for one week or longer within the prior 6 months Participants must be patients of the Calgary MS Clinic Participants must provide written informed consent  Participants who are pregnant or breastfeeding Participants in whom it is expected that their current DMT will be discontinued within 16 weeks. Indicators of likely discontinuation will poor DMT tolerance, a wish by the participant to discontinue the DMT, or a history of poor clinical response to the current DMT (such as a relapse within the previous year while on the current DMT) Participants who have a long QT interval, defined as corrected QT interval of more than 470 msec in men and more than 450 msec in women, on screening ECG Participants with known long-QT syndrome or known cardiac arrhythmia Participants who currently or previously have been treated with natalizumab Participants who are currently treated with domperidone or have taken it within the previous 3 months Participants who are taking drugs which prolong QT intervals or who are treated with drugs that inhibit cytochrome P450 3A4 Participants who are concurrently treated with drugs that may increase serum prolactin levels Participants who have a prolactinoma Participants who use systemic corticosteroids within the 8 weeks prior to the screening MRI or who use concurrent immunosuppressive medications including systemic corticosteroids