RITUXAN
Clinical safety rating
cautionComprehensive clinical and safety monograph for RITUXAN (RITUXAN).
Comprehensive clinical and safety monograph for RITUXAN (RITUXAN).
Non-Hodgkin lymphoma (NHL)Chronic lymphocytic leukemia (CLL)Rheumatoid arthritis (RA)Granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA)Pemphigus vulgarisOff-label: immune thrombocytopenia, autoimmune hemolytic anemia, multiple sclerosis, systemic lupus erythematosus
Rituximab is a chimeric monoclonal antibody that binds specifically to the CD20 antigen on pre-B and mature B-lymphocytes. Binding induces complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC), leading to B-cell depletion.
| Metabolism | Rituximab is a monoclonal antibody and is not metabolized by cytochrome P450 enzymes; it is degraded via catabolic pathways into small peptides and amino acids. |
| Excretion | Rituximab is eliminated primarily via reticuloendothelial system metabolism and target-mediated clearance. Renal excretion is negligible (<1% of dose as intact antibody in urine). Biliary/fecal excretion is minimal. Clearance is influenced by tumor burden and CD20 expression. |
| Half-life | Mean terminal elimination half-life is approximately 22 days (range 6.1–52 days) after first dose, decreasing to about 6 days after fourth dose due to target-mediated clearance. Clinical context: Extended half-life allows for weekly or every-2-week dosing; half-life shortens with repeated dosing due to B-cell depletion. |
| Protein binding | Rituximab is a monoclonal antibody; specific protein binding is not characterized. Binding to FcRn may influence half-life. No significant binding to plasma proteins other than antigen targets. |
| Volume of Distribution | Volume of distribution at steady state (Vdss) is approximately 3.1–4.5 L (0.04–0.06 L/kg for a 70 kg patient), indicating limited extravascular distribution, primarily confined to plasma and interstitial fluid. Clinical meaning: Low Vd reflects distribution mainly in central compartment; minimal penetration into tissues. In non-Hodgkin lymphoma, Vd may be higher due to tumor binding. |
| Bioavailability | Intravenous: 100% bioavailability. Not available for subcutaneous, intramuscular, or other routes; no oral formulation due to protein degradation. |
| Onset of Action | Intravenous: Onset of clinical effect (B-cell depletion) occurs within hours to days. Maximal B-cell depletion in peripheral blood is observed by 2–3 weeks after first infusion. Clinical response in rheumatoid arthritis may be seen within 8–16 weeks. |
| Duration of Action | Duration of B-cell depletion is 6–12 months after a single treatment course (e.g., 2 infusions). Clinical duration varies: in oncology, response may last months to years; in autoimmune conditions, retreatment is often needed every 6–12 months. Recovery of B-cell counts begins approximately 6 months after completion of therapy. |
| Molecular Weight | 144000 |
375 mg/m2 IV weekly for 4 doses for non-Hodgkin lymphoma; 1000 mg IV on days 1 and 15 for rheumatoid arthritis; 375 mg/m2 IV weekly for 4 doses for chronic lymphocytic leukemia (in combination with fludarabine and cyclophosphamide).
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment; not removed by hemodialysis. |
| Liver impairment | No specific guidelines for Child-Pugh; use caution in severe hepatic impairment as it has not been studied. |
| Pediatric use | Safety and efficacy not established in pediatric patients for most indications; use in pediatric nephrotic syndrome: 375 mg/m2 IV weekly for 4 doses. |
| Geriatric use | No specific dose adjustment; monitor for increased risk of infections and cardiac events. |
| 1st trimester | Rituximab is a monoclonal antibody that is actively transported across the placenta, especially during the third trimester. However, data in first trimester are limited; animal studies show no evidence of harm, but there are no adequate human studies. Use only if clearly needed and benefit outweighs risk. |
| 2nd trimester | Similar to T1, limited human data; potential for fetal B-cell depletion and lymphopenia. Monitor fetal effects if prolonged exposure. Use only if clearly needed. |
| 3rd trimester | Rituximab crosses the placenta readily in the third trimester, leading to neonatal B-cell depletion and lymphopenia. Avoid use if possible; if necessary, monitor neonate for infection risk and delayed vaccination. |
Clinical note
Comprehensive clinical and safety monograph for RITUXAN (RITUXAN).
| Placental transfer | Rituximab is a humanized IgG1 monoclonal antibody that actively crosses the placenta via FcRn-mediated transport, increasing in transfer as pregnancy progresses. It reaches fetal concentrations comparable to maternal levels in the third trimester, causing fetal B-cell depletion. |
| Breastfeeding | Rituximab is excreted into breast milk in very low concentrations (infant dose <0.1% of maternal dose). Due to its large molecular weight and oral bioavailability being negligible, systemic absorption in the infant is unlikely. However, data are limited; caution is advised. Consider discontinuing breastfeeding or drug based on importance to mother. |
| Lactation Rating | L3 - Moderately Safe (likely compatible, but caution advised) |
| Teratogenic Risk | First trimester: There is a theoretical risk based on mechanism (B-cell depletion), but human data are limited. Rituximab is an IgG1 antibody that crosses the placenta in the second and third trimesters, with highest fetal exposure in the third trimester. Second/third trimester: Cases of transient neonatal B-cell lymphopenia and cytopenias have been reported; however, no consistent pattern of major congenital malformations has been observed. Overall risk is considered low, but B-cell depletion in neonates is possible. |
| Fetal Monitoring | Maternal: Monitor for infusion reactions, infections, and cytopenias. Fetal/neonatal: If used after 20 weeks gestation, monitor neonatal complete blood count (CBC) at birth and for signs of infection or hematologic abnormalities. Because of the risk of B-cell depletion, avoid live vaccines in infants for at least 6 months after last maternal dose. |
| Fertility Effects | In women, rituximab may cause ovarian failure and reduced fertility based on cases of ovarian insufficiency reported in premenopausal women. In men, no specific effects on sperm have been documented; however, animal studies show no impairment of fertility. Effect on fertility appears to be reversible in some cases. |
■ FDA Black Box Warning
WARNING: Fatal infusion reactions, severe mucocutaneous reactions, progressive multifocal leukoencephalopathy (PML), and hepatitis B reactivation.
| Serious Effects |
Known hypersensitivity to rituximab or any of its excipientsActive severe infections (e.g., tuberculosis, sepsis, opportunistic infections)
| Precautions | Infusion reactions (fatal within 24 hours), tumor lysis syndrome, severe mucocutaneous reactions (e.g., Stevens-Johnson syndrome), hepatitis B reactivation (screen high-risk patients), progressive multifocal leukoencephalopathy (PML), cardiac arrhythmias, renal toxicity (in combination with chemotherapy), bowel obstruction/perforation, and vaccination limitations (live vaccines not recommended during treatment). |
| Food/Dietary | No known food interactions. No dietary restrictions required. |
| Clinical Pearls | Rituximab (RITUXAN) is a chimeric monoclonal antibody against CD20, used for B-cell malignancies and autoimmune diseases. Premedicate with acetaminophen, diphenhydramine, and a corticosteroid to reduce infusion reactions. Monitor for tumor lysis syndrome in high-tumor-burden patients. Hepatitis B reactivation can occur; screen all patients before therapy. Progressive multifocal leukoencephalopathy (PML) is a rare but fatal risk. Do not administer live vaccines during or after treatment until B-cell recovery. |
| Patient Advice | You may experience infusion reactions such as fever, chills, or rash; these are usually manageable with premedication. · Avoid live vaccines (e.g., MMR, shingles, yellow fever) during treatment and for at least 6 months after. · Report any signs of infection, including fever, cough, or painful urination, promptly. · Tell your doctor if you have a history of hepatitis B; this virus can reactivate and cause serious liver problems. · Use effective contraception during therapy and for 12 months after the last dose. · Do not drive or operate machinery if you experience dizziness or weakness after infusion. |
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