Comparing Risk and Severity of IRRs in Patients Premedicated With Cetirizine vs. Diphenhydramine Prior to Ocrelizumab

Inclusion Criteria:

Male or female patient with relapsing or progressive forms of Multiple Sclerosis (MS), age 18 to 70 inclusive at the time of consent.
Able to understand the purpose, responsibilities and risks of the study and provide signed informed consent.
Naïve to ocrelizumab (OCR) and will receive OCR as part of standard of care for MS treatment.
No evidence, in the opinion of the investigators of significant cognitive limitation or psychiatric disorder that would interfere with the conduct of the study.
Estimated Expanded Disability Status Scale (EDSS) of ≤ 6.5 at screening.
Female patients of childbearing potential must practice effective contraception and continue contraception during the study.

Exclusion Criteria:

Any mental condition of such that patient is unable to understand the nature, scope, and possible consequences of the study.
Evidence of active hepatitis B infection at screening.
Patients with untreated hepatitis C, or tuberculosis. Patients who have history of Progressive multifocal leukoencephalopathy (PML) or known to be Human Immunodeficiency Virus (HIV) positive, per standard care.
Any persistent or severe infection.
Pregnancy or lactation.
Significant, uncontrolled somatic disease or severe depression in the last year.
Current use of immunosuppressive medication, lymphocyte-depleting agents, or lymphocyte-trafficking blockers.
Patients with any significant comorbidity that in the opinion of the investigator, would interfere with participation in the study.
Any known allergy or inability to tolerate diphenhydramine or cetirizine.