Section 07 · Monograph
Rituximab
Reviewed Nov 2026FDA label
RituxanAnti-CD20 mAb
- Forms
- IV: 10mg/mL vial
- Dose
- Protocol-dependent (e.g. 375mg/m² weekly x4 or 1000mg x2)
- MOA
- Depletes CD20+ B-cells
Black Box Warning
- Fatal infusion reactions
- Severe mucocutaneous reactions
- Hepatitis B virus reactivation, which may cause fulminant hepatitis, hepatic failure, and death
- Progressive multifocal leukoencephalopathy (PML)
Indications
- Off-label use in relapsing and progressive forms of multiple sclerosis and neuromyelitis optica spectrum disorder (not FDA-approved for MS; commonly used off-label based on clinical evidence)FDA-labeled
Off-Label Uses
- Multiple sclerosis (relapsing and progressive forms)Off-label
- Neuromyelitis optica spectrum disorderOff-label
Mechanism of Action
- Chimeric monoclonal antibody against CD20 antigen on B lymphocytes
- Mediates B-cell lysis through complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity, and induction of apoptosis, depleting circulating B cells implicated in MS pathogenesis
Full Dosing
Adult / usual
- Off-label MS regimen varies: commonly 1000 mg IV on days 1 and 15, then either redosing every 6 months or based on B-cell repletion/CD19 counts
- Premedicate with glucocorticoid, acetaminophen, and antihistamine before each infusion
Contraindications
- Known hypersensitivity to rituximab or murine proteins
Drug Interactions
- Avoid live vaccines during and after B-cell depletion
- Additive immunosuppression with other immunosuppressive agents
Adverse Effects
- Infusion-related reactions (fever, chills, rigors)
- Infections (upper respiratory, urinary tract)
- Fatigue
- Hypogammaglobulinemia with repeated dosing
- Neutropenia (sometimes delayed)
- Rare: PML, hepatitis B reactivation
Monitoring Parameters
- Hepatitis B screening before initiation
- CBC with differential, including neutrophil counts, periodically
- Immunoglobulin levels with repeated courses
- CD19/CD20 B-cell counts to guide redosing
- Signs of infection during and after infusions
Pregnancy & Lactation
- Crosses placenta; may cause B-cell lymphopenia in neonates when used in pregnancy
- Consider pregnancy exposure registry
- Unknown if present in human milk; weigh benefits vs risks