Rituximab Initial Dosing Regimen
The recommended initial dosing regimen for rituximab is 375 mg/m² administered intravenously once weekly for 4 weeks, which is the standard across most indications including non-Hodgkin's lymphoma, ANCA-associated vasculitis, and idiopathic inflammatory myopathies. 1, 2, 3, 4
Standard Dosing by Indication
Non-Hodgkin's Lymphoma
- Administer rituximab 375 mg/m² IV weekly for 4 consecutive weeks as the standard induction regimen 1, 3, 4
- This applies to both indolent and aggressive subtypes, whether used as monotherapy or in combination with chemotherapy 1
- For elderly or infirm patients who cannot tolerate combination therapy, single-agent rituximab at this same dose is preferred 1, 2
Rheumatoid Arthritis and Autoimmune Conditions
- Administer 1000 mg IV on day 1, followed by 1000 mg IV on day 15 (two-dose regimen separated by 2 weeks) 5, 2, 4
- This regimen is also used for pemphigus vulgaris and has been validated in idiopathic inflammatory myopathies 5, 4
ANCA-Associated Vasculitis (GPA/MPA)
- For adults: 375 mg/m² IV once weekly for 4 weeks as induction therapy 2, 3, 4
- For pediatric patients: 375 mg/m² IV once weekly for 4 weeks 4
- Must be combined with glucocorticoids: methylprednisolone 1000 mg IV daily for 1-3 days (or 30 mg/kg for pediatrics, max 1g/day), followed by oral prednisone 4
Alternative Dosing Regimen
An alternative regimen of 375 mg/m² on week 1, followed by 500 mg/m² weekly for weeks 2-8 has been studied but showed no superiority over standard dosing 6. The standard 375 mg/m² weekly for 4 weeks remains preferred.
Essential Pre-Treatment Requirements
Before initiating rituximab, you must obtain:
- Baseline immunoglobulin levels (IgG, IgM, IgA) 5, 2, 3
- Hepatitis B and C antibody screening 5, 2, 3
- Latent tuberculosis screening 5, 2, 3
- Complete blood count with differential 2, 3
Mandatory Premedication Protocol
Administer 30-60 minutes before each infusion:
- Acetaminophen (antipyretic) 3, 4
- H1 antihistamine (diphenhydramine or equivalent) 3, 4
- For rheumatoid arthritis, vasculitis, and pemphigus vulgaris patients: add methylprednisolone 100 mg IV or equivalent 4
This premedication reduces infusion reactions, which occur in up to 77% of patients during the first infusion 3.
Critical Safety Monitoring
Infection Prophylaxis Requirements
- For CLL patients: Provide PCP and herpes virus prophylaxis during treatment and for up to 12 months after completion 4
- For GPA/MPA patients: Provide PCP prophylaxis during treatment and for at least 6 months following the last infusion 4
- For pemphigus vulgaris: Consider PCP prophylaxis during and after treatment 4
Ongoing Monitoring
- Monitor for hepatitis B reactivation throughout treatment 2, 3
- Watch for progressive multifocal leukoencephalopathy (PML), particularly in immunosuppressed patients 5, 2, 3
- Consider tumor lysis syndrome prophylaxis in high-risk patients (high tumor burden) 1, 2
Administration Technique
- Dilute rituximab to a final concentration of 1-4 mg/mL in 0.9% sodium chloride or 5% dextrose 4
- First infusion: Start slowly due to high risk of infusion reactions 4
- For Grade 1-2 infusion reactions: Slow or temporarily stop the infusion and provide symptomatic treatment 3
- For Grade 3-4 reactions: Stop the infusion immediately and provide aggressive symptomatic treatment 3
Common Pitfalls to Avoid
Do not skip premedication, even for subsequent infusions—infusion reactions can occur at any time, though they are most common during the first infusion 3, 4.
Do not overlook hepatitis B screening—reactivation can be fatal and occurs even in patients with resolved infection 2, 3.
Do not use rituximab without PCP prophylaxis in high-risk populations (CLL, vasculitis patients on multiple immunosuppressants) 4.
The thrice-weekly dosing schedule studied in CLL (100 mg initial dose, then 375 mg/m² three times weekly) showed activity but is not standard practice 7. Stick with the weekly × 4 weeks regimen unless treating a specific protocol-driven indication.