Rituximab Dosing Regimens and Follow-up Recommendations
The recommended rituximab dosing regimen is 1000 mg administered on days 1 and 15, or alternatively 375 mg/m² once weekly for 4 weeks, with follow-up monitoring including baseline immunoglobulin levels, hepatitis B and C screening, and latent tuberculosis screening prior to administration. 1
Standard Dosing Regimens
- For idiopathic inflammatory myopathies: Rituximab 1000 mg repeated on day 15, or 375 mg/m² once weekly for 4 weeks 1
- For Waldenström's macroglobulinemia: Rituximab 375 mg/m² weekly for 4 cycles, often combined with other agents 1
- For diffuse large B-cell lymphoma: Rituximab 375 mg/m² per cycle when combined with CHOP chemotherapy 1
- For membranous nephropathy: Two commonly used approaches are 2 bi-weekly doses of 1 g or 4 weekly doses of 375 mg/m², which appear to be clinically equivalent 1
Disease-Specific Considerations
Inflammatory Myopathies
- The Rituximab in Myositis study showed favorable response in 83% of patients with refractory disease throughout a 44-week trial 1
- For adults, administer two 1000 mg doses of rituximab 2 weeks apart 1
Waldenström's Macroglobulinemia
- When combined with bortezomib: Rituximab 375 mg/m² at each cycle during 4 cycles 1
- When used in combination regimens like DRC (dexamethasone, rituximab, cyclophosphamide): Rituximab 375 mg/m² IV on day 1 1
- IgM flare is a common concern when initiating therapy and should be monitored 1
Maintenance Therapy
- For ANCA-associated vasculitis: Maintenance dosing of rituximab every 6 months is a common protocol 2, 3
- For refractory conditions: Increasing rituximab frequency to every 3-4 months may be necessary when patients experience disease flares before the next scheduled dose 2
- For pediatric GPA/MPA: Some patients receive four once-weekly doses (375 mg/m²) approximately every 6 months for maintenance 4
Pre-Treatment Assessment and Monitoring
- Obtain baseline immunoglobulin levels (IgG, IgM, IgA) 1
- Determine hepatitis B and C antibody status 1
- Screen for latent tuberculosis prior to administering rituximab 1
- Monitor white blood cell count when combined with cytotoxic agents 1
Safety Considerations
- Severe infectious complications are a concern, particularly in immunosuppressed patients 1
- Progressive multifocal leukoencephalopathy has been reported in rheumatic patients treated with rituximab; use caution in immunosuppressed patients 1
- Infusion-related reactions occur in the majority of patients but are usually mild to moderate flu-like symptoms that decrease with subsequent infusions 5
- Approximately 10% of patients may develop severe infusion-related reactions (bronchospasm, hypotension) 5
Follow-up Recommendations
- Monitor complete blood count with differential at baseline and at 2-4 month intervals during treatment 2
- Assess clinical response through disease-specific parameters (e.g., muscle strength in myositis, IgM levels in Waldenström's) 1
- For lymphoma patients, FDG-PET/CT is the recommended standard for post-treatment assessment 1
- In patients with refractory disease who relapse, repeated cycles of rituximab can be effective 6, 3
Common Pitfalls and Caveats
- IgA deficiency should be assessed, as patients with this condition may experience severe anaphylaxis with IgA-containing products 1
- Prophylaxis against herpes zoster is strongly recommended for patients receiving rituximab with proteasome inhibitors 1
- Avoid rituximab in patients with active hepatitis B infection due to risk of reactivation 1
- The response to rituximab may be delayed in some conditions, with progressive reduction of disease markers occurring over several months 1