What is the recommended dose of Rituximab (rituximab) for treating hypersensitivity pneumonitis?

Rituximab Dosing for Hypersensitivity Pneumonitis

For patients with hypersensitivity pneumonitis requiring rituximab therapy, the recommended dose is 1000 mg administered intravenously on day 1 and day 15, or alternatively 375 mg/m² once weekly for 4 weeks. 1

Dosing Regimens

• Two standard dosing regimens are used for rituximab in hypersensitivity pneumonitis:

  • Fixed dose regimen: 1000 mg IV on day 1 and repeated on day 15 1
  • BSA-based regimen: 375 mg/m² IV once weekly for 4 weeks 1

• For maintenance therapy in refractory cases, rituximab may be repeated as needed based on clinical response, typically every 24 weeks 1

Patient Selection and Considerations

• Rituximab is primarily used as salvage therapy for refractory hypersensitivity pneumonitis that has not responded to standard immunosuppressive therapy 2

• Before initiating rituximab therapy, obtain:

  • Baseline immunoglobulin levels (IgG, IgM, IgA)
  • Hepatitis B and C antibody screening
  • Latent tuberculosis screening 1

• Monitor complete blood count with differential at baseline and at 2-4 month intervals during treatment 1

Administration and Monitoring

• Premedication is recommended to reduce infusion reactions:

  • Antipyretic (e.g., acetaminophen)
  • Antihistamine (e.g., diphenhydramine) 1

• Monitor closely for infusion reactions, which occur in up to 77% of patients during the first infusion 1

• Infusion reactions management:

  • For Grade 1/2 reactions: Slow or temporarily stop the infusion and provide symptomatic treatment
  • For Grade 3/4 reactions: Stop the infusion, provide aggressive symptomatic treatment, and consider permanent discontinuation 1

Safety Considerations

• Common adverse effects include:

  • Infusion-related reactions (fever, chills, rigors)
  • Cytopenias
  • Increased risk of infections 1

• Serious adverse events to monitor:

  • Progressive multifocal leukoencephalopathy (rare but serious)
  • Hepatitis B reactivation
  • Severe infections 1

• Rituximab-induced lung injury is a rare but potentially serious complication that requires a high index of suspicion 3, 4

Efficacy in Hypersensitivity Pneumonitis

• A retrospective study of 20 patients with chronic hypersensitivity pneumonitis showed:

  • Stabilization of forced vital capacity (FVC) after 6 months of rituximab therapy
  • Significant reduction in the rate of FVC decline compared to pre-treatment period
  • Stable diffusion capacity (DLCO) with improvement in 63% of patients 5

• Consider rituximab particularly for patients with:

  • Progressive disease despite antigen avoidance
  • Failure of standard immunosuppressive therapy
  • High risk of mortality from progressive disease 2, 5

Hypersensitivity to Rituximab

• For patients who develop hypersensitivity to rituximab:
  • Desensitization protocols may allow continued treatment
  • Skin testing may be performed but has limited predictive value for reactions
  • Elevated tryptase levels during reactions suggest mast cell involvement 6