• Rituximab may be used to treat non-Hodgkin's lymphoma (NHL), chronic lymphocytic leukemia (CLL), rheumatoid arthritis (RA), and some other conditions.
• Rituximab works by targeting a specific protein, called CD20, that exists on the surface of immature and mature B-lymphocytes. B lymphocytes are a type of white blood cell that are thought to contribute to the development of certain inflammatory conditions that affect B-cells. When rituximab binds to this protein, it causes B-cells to self-destruct or disintegrate. NHL and CLL are blood cancers that affect B-cells. CD20 is an antigen that is displayed on certain B-cells, providing a target for rituximab to latch onto. However, the exact way rituximab works is not completely clear. Studies suggest that rituximab may recruit macrophages, which are also a type of white blood cell, to ‘eat’ the B-cells via a process called antibody-dependent phagocytosis. It may also bring about antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity.
• Rituximab depletes B-cells, which can cause swelling and joint damage in people with autoimmune disorders, such as rheumatoid arthritis and the autoimmune disorders granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). Instead of producing helpful antibodies to fight off invaders, B-cells in people with GPA and MPA are thought to produce harmful inflammation-causing auto-antibodies. By reducing the number of B-cells, rituximab helps limit the production of auto-antibodies.
• Rituximab belongs to the class of medicines called CD20 monoclonal antibodies. It may also be called a targeted treatment, a biologic, or a monoclonal antibody.

• May be used to treat adults with relapsed or refractory, low-grade or follicular, CD20-positive, B-cell non–Hodgkin's lymphoma (NHL) as a sole agent.
• May be used to treat previously untreated follicular, CD20-positive, B-cell NHL in combination with first-line chemotherapy. In those who achieve a complete or partial response, it may be continued as single-agent maintenance therapy.
• For non-progressing (including stable disease), low-grade, CD20-positive, B-cell NHL it may be given as a single agent after first-line cyclophosphamide, vincristine, and prednisone (CVP) chemotherapy.
• For previously untreated, diffuse large B-cell, CD20-positive NHL, rituximab may be given in combination with cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP), or other anthracycline-based chemotherapy regimens.
• May be given to adults with previously untreated or previously treated CD20-positive chronic lymphocytic leukemia (CLL) in combination with fludarabine and cyclophosphamide.
• May be used in adults with moderately-to-severely active rheumatoid arthritis who have had an inadequate response to one or more TNF antagonist therapies in combination with methotrexate.
• Can be given to adults and children aged 2 years of age and older with Granulomatosis with Polyangiitis (GPA) (Wegener's Granulomatosis) and Microscopic Polyangiitis (MPA) in combination with glucocorticoids.
• Approved to treat adults with moderate to severe pemphigus vulgaris.
• Available in two strengths: 100 mg/10 mL (10 mg/mL) and 500 mg/50 mL (10 mg/mL) in a single-dose vial.
• Rituximab is not chemotherapy, it is a targeted treatment that works by binding to a protein called CD20 that is present on the surface of B-lymphocytes, which are a type of white blood cell. When rituximab binds to this protein, it causes B-cells to self-destruct or disintegrate.

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• Infusion-related reactions, fever, lymphopenia, neutropenia, chills, infection, pain, night sweats, rash, itch, and asthenia are the most common side effects reported. Lymphopenia, leukopenia, neutropenia, thrombocytopenia, and anemia may also occur. Other side effects include cough, bronchospasm, nausea, diarrhea, vomiting, and muscle and joint aches and pains.
• Infusion-related reactions can be fatal. These usually occur during the first infusion with a time to onset of 30–120 minutes and symptoms include urticaria, low blood pressure, angioedema, hypoxia, bronchospasm, pulmonary infiltrates, acute respiratory distress syndrome, myocardial infarction, ventricular fibrillation, cardiogenic shock, anaphylactoid events, or death.
• Cardiac adverse reactions, including ventricular fibrillation, myocardial infarction, and cardiogenic shock may occur in patients receiving rituximab. Perform cardiac monitoring during and after all infusions of rituximab for patients who develop clinically significant arrhythmias, or who have a history of arrhythmia or angina and discontinue infusions for serious or life-threatening cardiac arrhythmias.
• Severe, including fatal, renal toxicity can occur after rituximab administration in patients with NHL.
• Abdominal pain, bowel obstruction, and perforation, in some cases leading to death, can occur in patients receiving rituximab in combination with chemotherapy. The average time to onset was 6 days (range 1–77) days in patients with NHL.
• Must be administered via an intravenous infusion by a healthcare professional with facilities to manage severe infusion-related reactions. Cannot be administered via an IV push or bolus. The dosage and rate of infusion vary depending on the condition being treated and how well tolerated the infusion is.
• Patients need to be premedicated with acetaminophen and an antihistamine before each infusion to lower the risk of infusion-related reactions. For those receiving a glucocorticoid as part of their chemotherapy regimen, this should be administered before the infusion.
• For RA, GPA, MPA, and PV patients, methylprednisolone 100mg IV should be administered 30 minutes before the infusion.
• Patients with CLL have a higher risk of developing herpes virus infections and Pneumocystis jirovecii pneumonia (PCP) during treatment and for 12 months following treatment and should be provided with prophylactic treatment for both these infections. PCP prophylaxis is also recommended for those with GPA and MPA during treatment and for at least 6 months after the last rituximab infusion and should be considered for those with PV.
• Reactivation of hepatitis B has been reported in people who have a current or prior hepatitis B virus (HBV) infection before initiating treatment with rituximab. In some cases, this has resulted in severe and rapid liver disease, hepatic failure, and death. All patients should be screened for current or prior hepatitis B virus (HBV) infection by measuring HBsAg and anti-HBc before initiating treatment with rituximab.
• A complete blood count (CBC) including platelets is also needed before the first dose. Depending on the condition being treated, CBCs with differential and platelets may be needed before every infusion, at weekly or monthly intervals, and more frequently in those who develop cytopenias. Continue to monitor for cytopenias after the final dose and until resolution.
• Rituximab should be initiated at an infusion rate of 50 mg/h. Provided there are no serious infusion reactions, the infusion rate may be increased by 50 mg/h increments every 30 minutes, to a maximum of 400 mg/h. For subsequent infusions, start at a rate of 100 mg/h and increase by 100 mg/h increments at 30-minute intervals to a maximum of 400 mg/h. Interrupt the infusion or slow the infusion rate for infusion-related reactions. Continue the infusion at one-half the previous rate upon the improvement of symptoms.
• For patients with previously untreated follicular NHL and DLBCL patients who did not experience a Grade 3 or 4 infusion-related adverse event during Cycle 1, a 90-minute infusion can be administered in Cycle 2 with a glucocorticoid-containing chemotherapy regimen. Start at a rate of 20% of the total dose in the first 30 minutes and the remaining 80% of the total dose given over the next 60 minutes. If this 90-minute infusion is tolerated in Cycle 2, the same rate can be used when administering the remainder of the treatment regimen (through Cycle 6 or 8). Do not administer this 90-minute rate to those with clinically significant cardiovascular disease or who have a circulating lymphocyte count ≥5,000/mm3 before Cycle 2.
• Serious infections, including sepsis, occurred in less than 5% of patients with NHL. The overall incidence of infections was 31% (bacterial 19%, viral 10%, unknown 6%, and fungal 1%).
• Mucocutaneous reactions, some fatal, such as paraneoplastic pemphigus, Stevens-Johnson syndrome, lichenoid dermatitis, vesiculobullous dermatitis, and toxic epidermal necrolysis have occurred in people treated with rituximab. Discontinue treatment.
• Rituximab will suppress the immune system and will reduce a person's ability to fight infection. This ability will be further compromised if the person is also taking other drugs that suppress the immune system, such as chemotherapy agents, immune-modulating therapies, or other immunosuppressants. This immune-suppressing effect will persist for a few months after stopping rituximab treatment. Review all other immune-suppressing medications before initiating rituximab, and be aware of those with a long half-life whose effects may persist for weeks after discontinuation, such as natalizumab, teriflunomide, or mitoxantrone. Life-threatening and fatal infections have occurred in association with rituximab.
• Rituximab will also reduce the immune response to live vaccines, such as MMR and varicella vaccines. All vaccines should be up to date before rituximab is even started. Administer all live or live-attenuated vaccines at least 4 weeks before initiating rituximab, and non-live vaccines at least 2 weeks before.
• Cases of progressive multifocal leukoencephalopathy (PML) have occurred in patients with hematologic malignancies or with autoimmune diseases who have received rituximab. PML is an opportunistic viral infection of the brain caused by the JC virus (JCV) that often leads to death or severe disability. Posterior reversible encephalopathy syndrome (PRES), tumor lysis syndrome (TLS), and respiratory effects have also been reported.
• The use of rituximab in patients with RA who have responded to TNF antagonists has not been studied and is not recommended.
• Can cause fetal harm if administered to pregnant women and those of childbearing potential should use effective contraception while receiving rituximab and for 12 months after the last dose. If a woman becomes inadvertently pregnant she should advise her doctor immediately. Women should not breastfeed during treatment with rituximab and for 6 months after the last dose.
• Not available as a generic but is available under the brand name Rituxan.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

• Before starting treatment with rituximab, and during treatment with rituximab, tell your health care provider if you think you have an infection or have symptoms of an infection such as a fever, chills, muscle aches, cough, shortness of breath, runny nose, sore throat, red or painful skin or sores on your body, tiredness, or pain during urination. Also, let them know if you have infections that keep coming back.
• Some vaccinations may need to be avoided during treatment with rituximab and for a few months after stopping it. Take care to avoid people who are unwell and protect yourself from injury.
• Your doctor will also obtain a complete blood count including platelets and screen you for hepatitis B virus (HBV) infection before starting rituximab. This is because treating HCV may reactivate an underlying hepatitis B infection (HBV). Any underlying HBV infection should be treated before rituximab is started.
• Your first infusion of rituximab will be given slowly to see how well you tolerate it. Your actual appointment time will be longer because premedication with acetaminophen, an antihistamine, and sometimes a glucocorticoid needs to be administered 30 to 60 minutes before giving rituximab, to lessen the risk of an infusion reaction happening.
• Infusion reactions, some serious, may occur while you are having a rituximab infusion. Symptoms may include itchy skin, a rash, hives, skin redness, bronchospasm, throat irritation, oropharyngeal pain, shortness of breath, throat edema, flushing, low blood pressure, fever, fatigue, headache, dizziness, nausea, a fast heartbeat, and anaphylaxis.
• Tell your doctor if you are pregnant, intending to become pregnant, or breastfeeding before being administered rituximab as it is not suitable during pregnancy and breastfeeding. Use effective contraception while receiving rituximab and for 12 months after the last infusion. If you inadvertently become pregnant, see your doctor immediately.

• Starts working rapidly in patients with non-Hodgkin’s lymphoma. An initial clinical trial showed CD20+ B-cells were rapidly depleted in the peripheral blood of patients 24-72 hours after they received rituximab. Tumor biopsies taken 2 weeks after treatment with rituximab revealed that the drug had attached itself to tumor cells and the number of B-cells had decreased. Further investigation also confirmed that B-cells were depleted within the first 3 weeks.
• In addition to these immediate effects of rituximab on the body, researchers have investigated how long it takes for the drug to cause signs of cancer to decrease and disappear. In a key clinical trial conducted on 166 patients with NHL, the median time to onset of response was 50 days in the 48% of patients who responded to therapy.
• Rituximab also works in the same way to cause a rapid depletion of B-cells in patients with CLL.
• Rituximab also rapidly depletes B-cells from the blood circulation in patients with rheumatoid arthritis. One dose of rituximab is enough to deplete a patient’s B-cells. An important point to note; however, is that rituximab works slower - has a slower onset of action - in people with rheumatoid arthritis compared with other biological DMARD (disease-modifying anti-rheumatic drugs). Patients treated with rituximab may notice an early response within 8 weeks of treatment, but this is generally transient and due to the glucocorticoid pre-medication given alongside the rituximab infusion. Most rheumatoid arthritis patients will notice some improvement in their symptoms, such as improvement in their levels of pain and inflammation, within 16 weeks of starting treatment with rituximab.

Medicines that interact with rituximab may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with rituximab. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with rituximab include:

• antineoplastics, such as capecitabine or cyclophosphamide
• antipsychotics, such as clozapine
• biologics, such as adalimumab, etanercept, golimumab, or infliximab
• fingolimod or golimumab
• HIV medications, such as zidovudine
• immunosuppressants such as azathioprine, cyclosporine, or tacrolimus
• interferon
• live vaccines and some other vaccines, such as BCG, cholera, Covid-19 vaccines, measles, hepatitis b vaccines, yellow fever, or live influenza vaccines (rituximab reduces the immune response to vaccination. Administer live or live-attenuated vaccines at least 4 weeks before rituximab initiation, and non-live vaccines at least 2 weeks before)
• probiotics, such as bifidobacterium or lactobacillus
• zinc.

Rituximab may have additive immune-suppressing effects when given with any other medications such as anticancer drugs, immune-modulating, or immunosuppressive therapies, which may increase a person's risk for infection. Take this into account when switching from drugs with prolonged immune effects.

Note that this list is not all-inclusive and includes only common medications that may interact with rituximab. You should refer to the prescribing information for rituximab for a complete list of interactions.