Generic Name

Rituxan

Mechanism

• Targeting: Binds selectively to CD20, a glycoprotein expressed on pre‑B and mature B cells.
• B‑cell depletion: Induces antibody‑dependent cell‑mediated cytotoxicity (ADCC), complement‑mediated cytotoxicity, and apoptosis.
• Result: Reduces circulating and infiltrating B cells, diminishing autoantibody production and malignant proliferation.

Pharmacokinetics

• Absorption: Intravenous infusion; not administered orally.
• Distribution: Widely distributed in plasma and extravascular compartments; ~4% bound to plasma proteins.
• Metabolism: Cleaved by proteolytic enzymes to peptides and amino acids.
• Elimination: Primarily through the reticuloendothelial system; elimination half‑life ≈ 22–25 days (exponential decay).
• Special populations: No dose adjustment for mild–moderate renal or hepatic impairment; caution in severe renal impairment (excretion may be reduced).

Indications

• Non‑Hodgkin’s lymphoma (especially CD20⁺ subtypes)
• Chronic lymphocytic leukemia (CLL)
• Rheumatoid arthritis (RA) – as adjunct to methotrexate
• Granulomatosis with polyangiitis (GPA)
• Microscopic polyangiitis (MPA)
• IgG4‑related disease (off‑label)
• Autoimmune hemolytic anemia (off‑label)

Contraindications

• Allergy: Known hypersensitivity to rituximab or murine components.
• Active infections: Untreated bacterial, fungal, or viral infections (HBV reactivation risk).
• Immunocompromise: Severe neutropenia or concurrent immunosuppressive therapy.
• Cardiac risk: Concomitant atrial fibrillation or severe cardiac disease; monitor for infusion‑related cardiogenic events.
• Premature release warning: Subsequent dose availability delays could lead to suboptimal outcomes.

Dosing

• Standard regimen (e.g., for RA or NHL):
• 500 mg/m² IV infusion:
• 1st infusion: 60 min
• 2nd infusion: 30 min
• 2nd dose (week 2): same schedule
• Repeat cycles: Every 2–6 months depending on indication
• Lymphoma protocol (e.g., CHOP‑R):
• 375 mg/m² IV on day 1, repeated every 21 days for 6–8 cycles
• Infusion precautions:
• Pre‑medication with antihistamine, acetaminophen, methylprednisolone
• Slow infusion rate (≥ 2 h for first dose)
• Monitor vitals and symptomatology throughout.

Adverse Effects

Monitoring

• Baseline:
• CBC with differential, CMP, LFTs, urinalysis
• Viral serology (HBV, HCV, HIV)
• During therapy:
• Vital signs and infusion reaction observation
• CBC monthly (or per protocol)
• Serum creatinine & LFTs baseline to quarterly
• Anti‑CD20 B‑cell counts (optional) if objective is remission
• Post‑therapy:
• Monitor for delayed toxicities such as late infections or hypogammaglobulinemia
• Immunoglobulin levels if prolonged B‑cell depletion

Clinical Pearls

• Re‑infusion schedule matters: Delaying subsequent doses by > 6 weeks may diminish remission durability, especially in aggressive lymphomas.
• Immune reconstitution: B‑cell recovery typically occurs after 6–12 months; monitor IgG levels if prolonged hypogammaglobulinemia suspected.
• HBV prophylaxis: Universal prophylactic lamivudine or entecavir for HBV‑positive patients > 3 months pre‑rituximab.
• Infusion reaction mitigation: For patients with high risk, consider a pre‑infusion course of steroids, antihistamines, and a briefer infusion rate; subsequent infusions can often be accelerated safely.
• Autoimmune enthusiasm: Rituximab in GPA and MPA achieves remission in ~70 % of patients; early transition to maintenance therapy is key.
• Cross‑reactivity caution: Do not mix rituximab with other anti‑CD20 agents (e.g., ofatumumab) within 4 weeks without specialist review due to overlapping immunosuppression.

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• Keywords: rituximab, Rituxan pharmacology, non-Hodgkin lymphoma therapy, autoimmune disease treatment, B‑cell depletion, infusion reactions, dosing schedule, adverse effects, monitoring.