TRUXIMA
Clinical safety rating: caution
Truxima (rituximab-abbs) is a biosimilar CD20-directed cytolytic antibody used in the treatment of non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis, granulomatosis with polyangiitis, and microscopic polyangiitis. It is a key component of chemoimmunotherapy regimens and biologic therapy for autoimmune conditions, offering a targeted B-cell depletion approach.
TRUXIMA (rituximab-abbs) is a chimeric murine/human monoclonal IgG1 kappa antibody that binds specifically to the CD20 antigen on B-lymphocytes. It mediates B-cell lysis via complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC).
| Metabolism | Rituximab-abbs is a monoclonal antibody not metabolized by cytochrome P450 enzymes; elimination occurs via intracellular catabolism and target-mediated clearance. |
| Excretion | Primarily eliminated via reticuloendothelial system and target-mediated clearance. Renal excretion is minimal (<1% unchanged in urine) due to large molecular weight. Biliary/fecal excretion accounts for <5%. |
| Half-life | Mean terminal elimination half-life is approximately 21 days (range 14.4–38.7 days) in clinical studies for rheumatoid arthritis. Longer half-life observed in patients with lower tumor burden. Clinical context: supports weight-based dosing every 6 months. |
| Protein binding | Approximately 85–95% bound to plasma proteins, primarily alpha-2-macroglobulin and complement components. |
| Volume of Distribution | Vd approximately 0.1–0.15 L/kg for rituximab (TRUXIMA is a rituximab biosimilar). Clinical meaning: limited to vascular and interstitial spaces, negligible distribution into tissues. |
| Bioavailability | Subcutaneous: approximately 90% relative to intravenous (based on area under curve). Intravenous: 100%. |
| Onset of Action | Subcutaneous: Clinical effect (improvement in signs/symptoms) observed within 4–8 weeks after first dose. Intravenous: Similar onset, within 4–8 weeks. |
| Duration of Action | Duration of effect persists for approximately 6 months after a single dose, corresponding to sustained serum concentrations above therapeutic threshold. Clinical notes: retreatment recommended at 6-month intervals based on disease activity. |
{"non-Hodgkin’s_lymphoma":"375 mg/m² IV weekly for 4 or 8 doses, depending on regimen. May be combined with chemotherapy; premedicate with acetaminophen and an antihistamine.","chronic_lymphocytic_leukemia":"Day 0 of first cycle: 375 mg/m² IV. Cycles 2–6: 500 mg/m² IV on day 1, in combination with fludarabine and cyclophosphamide. Repeat every 28 days.","rheumatoid_arthritis":"Two 1000 mg IV infusions separated by 2 weeks, in combination with methotrexate. Subsequent courses may be given every 16–24 weeks based on clinical response; premedicate with methylprednisolone 100 mg IV or equivalent glucocorticoid.","granulomatosis_with_polyangiitis_and_microscopic_polyangiitis":"375 mg/m² IV weekly for 4 weeks, in combination with glucocorticoids. Premedicate with methylprednisolone and an antihistamine."}
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment is required in patients with renal impairment. Rituximab is not cleared renally. |
| Liver impairment | No formal pharmacokinetic studies have been conducted in patients with hepatic impairment. No dosage adjustment is recommended. |
| Pediatric use | Safety and effectiveness have not been established in pediatric patients. Not currently indicated for use in children. |
| Geriatric use |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Rituximab may cause fetal B-cell lymphocytopenia. Limited human data are available; in animal studies, rituximab crossed the placenta and caused B-cell depletion in offspring. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.
| Placental transfer | Rituximab is an IgG1 monoclonal antibody and is known to cross the placenta, especially during the second and third trimesters. Fetal serum concentrations can approximate maternal levels, leading to B-cell depletion and potential immune dysfunction in the neonate. |
| Breastfeeding | Presence in human milk unknown; IgG antibodies likely excreted in colostrum. M/P ratio: Not determined. Consider risks of infant exposure versus benefits of breastfeeding. |
■ FDA Black Box Warning
Fatal infusion reactions, severe mucocutaneous reactions, progressive multifocal leukoencephalopathy (PML), and hepatitis B reactivation with fulminant hepatitis have been reported. Patients should be monitored closely during therapy.
| Common Effects | Infusion-related reactions (fever, chills, rigors, urticaria, pruritus, bronchospasm, hypotension), Fatigue, Nausea, Headache, Upper respiratory tract infection, Neutropenia, Thrombocytopenia, Anemia, Rash, Diarrhea, Peripheral edema, Cough |
| Serious Effects | Fatal infusion reactionsSevere cytopenias (Grade 3–4 neutropenia, thrombocytopenia, anemia)Tumor lysis syndromeFulminant hepatitis B reactivationProgressive multifocal leukoencephalopathy (PML)Severe infections (sepsis, pneumonia, meningitis, hepatitis)Cardiac arrhythmias and heart failureSevere mucocutaneous reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis)Acute renal failure |
Known hypersensitivity to rituximab-abbs or any component of the formulation, active severe infections, and severe immunodeficiency (e.g., HIV with low CD4 count, congenital immunodeficiency). Relative contraindication: live vaccines during therapy.
| Precautions |
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| No dose adjustment based on age alone is necessary. However, geriatric patients may be at increased risk for infections and cardiac adverse events; monitor closely. |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: IgG antibodies cross placenta; limited human data suggests no increased risk of major malformations. Second and third trimesters: Potential for fetal B-cell depletion and cytopenias; risk of infection in neonates. Avoid use unless benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal complete blood counts with differential and lymphocyte subsets prior to and during therapy. For pregnancy, assess fetal growth via ultrasound; evaluate neonate for B-cell count, infections, and vaccination response for 6 months after last dose. |
| Fertility Effects | Animal studies show no impairment of fertility. In humans, no adequate data on fertility effects; rituximab may cause prolonged B-cell depletion and impact reproductive planning. |
| Infusion reactions (may be severe or fatal), tumor lysis syndrome (in patients with high tumor burden), serious infections (including bacterial, fungal, and viral), cardiac arrhythmias and angina, bowel obstruction/perforation, renal toxicity in patients with autoimmune diseases, and immunogenicity leading to hypersensitivity reactions. |