Rituximab (Rituxan, MabThera and biosimilar brands)

Medicine at a glance

• Generic name: rituximab, a CD20-targeted monoclonal antibody.
• Reference brands: Rituxan and MabThera. Verified biosimilar brands include Truxima, Ruxience, Riabni, Rixathon, Riximyo and Zimrixby.
• Routes: intravenous infusion, meaning a drip into a vein; selected patients can subsequently receive a subcutaneous injection, meaning under the skin.
• Subcutaneous products: Rituxan Hycela contains rituximab with hyaluronidase; European MabThera also has dedicated subcutaneous formulations containing hyaluronidase.
• Important precautions: administration reactions, hepatitis B reactivation, serious infections, low blood counts and rare serious neurological or skin reactions.

A biosimilar is a biological medicine shown to be highly similar to its reference medicine, without clinically meaningful differences in safety or effectiveness. The team selects the prescribed product and records its brand. An infusion product and an under-the-skin product are not interchangeable milligram for milligram. Overseas brand verification does not establish local availability.

What rituximab is and how it works

Rituximab attaches to CD20, a protein on certain B cells. B cells are a type of white blood cell, and some cancers develop from them. Binding to CD20 helps the immune system destroy these cells and can trigger processes leading to cell death. Treatment also removes some healthy B cells, which explains why protection against infection can be reduced.

It is a targeted antibody rather than conventional chemotherapy. Because it recruits immune mechanisms, it may also be described as immunotherapy, but it is not a checkpoint inhibitor. These terms describe different aspects of its action.

Rituximab may be prescribed alone, alongside other cancer medicines or as maintenance treatment intended to sustain disease control after an initial response. The accompanying medicines change the likely side effects and protective treatment needed. This article focuses on cancer care, rather than rituximab schedules for non-cancer conditions.

How the team decides whether it is suitable

Your oncologist considers the diagnosis, test results, previous treatment, disease activity, overall health and applicable prescribing information. Testing a biopsy or blood sample for CD20 helps establish whether the target is present. Finding CD20 does not by itself determine the whole treatment plan.

The team reviews infection history, hepatitis B results, immune function, heart and lung problems, and any previous reaction to an antibody treatment. A large amount of cancer or many cancer cells in the blood may increase the risk of an early reaction or tumour lysis syndrome, explained below.

Subcutaneous treatment is an option only for suitable regimens after a full intravenous dose has been successfully administered. It is not a way to bypass an intolerable first infusion. Some intravenous products have specialist paediatric cancer schedules; the fixed-dose subcutaneous products discussed here are adult treatments.

Before treatment starts

Tell the team about current fever, cough, diarrhoea, dental infection, shingles, recurrent infections, hepatitis, tuberculosis exposure, heart disease, breathing problems and previous severe allergies. Mention pregnancy possibilities, breastfeeding and any plans to have children. Bring all prescription, over-the-counter and herbal medicines.

Hepatitis B and immune checks

Everyone needs hepatitis B screening before rituximab. The product information specifies at least hepatitis B surface antigen, or HBsAg, and core antibody, or anti-HBc. Additional tests, including surface antibody and viral DNA, may be needed. An infection from many years ago can reactivate even if it seemed to have cleared and you feel well.

Active severe infection prevents treatment until appropriately managed. European information also prohibits treatment with active hepatitis B disease. A positive hepatitis result requires a specialist prevention and monitoring plan. Antiviral preventive treatment is generally recommended for patients with past hepatitis B receiving high-risk anti-CD20 therapy. ASCO guidance recommends continuing prevention for at least 12 months after the cancer treatment in this situation, with further management individualised. Your specialist may advise longer. Do not stop the antiviral when the last rituximab appointment ends.

Baseline tests include blood counts, kidney and liver function and relevant blood salts. Immunoglobulins, the antibodies that help protect against infection, may be measured; European intravenous information recommends checking them before treatment. The team reviews vaccination status and assesses whether additional heart or lung checks are needed.

Medicines to reduce early risks

Paracetamol and an antihistamine are normally given before each administration. A steroid may also be required, depending on the product and accompanying regimen. If tumour lysis risk is high, you may need extra fluids, a medicine to reduce uric acid and closer blood testing.

Blood pressure can fall during treatment. Your team may ask you to omit certain blood-pressure tablets for a specified period, sometimes 12 hours before an infusion. Obtain instructions about which tablets and when to restart; do not stop them independently.

How treatment is given

Intravenous infusion

A nurse gives rituximab through a cannula or central line in a unit equipped to manage reactions. It is not given as a rapid intravenous push. The first infusion starts slowly, with the rate increased only if you are tolerating it. Allow several hours and extra time for checks and observation. Later infusions may be quicker.

Doses are commonly calculated from body surface area, which uses height and weight. A common oncology dose is 375 mg per square metre; some schedules use 500 mg per square metre after the first cycle. These examples are not interchangeable prescriptions. The diagnosis, regimen, age and product determine the dose.

Selected adults may receive a 90-minute infusion from a later cycle under an approved protocol. This requires assessment of the previous reaction, heart health, blood-cell count and accompanying treatment; it is not the standard first infusion or appropriate for everyone.

Under-the-skin injection

Before switching, you must have received at least one full intravenous rituximab dose successfully. The US Hycela information also specifies without severe adverse reactions. If the full dose could not be completed, subsequent treatment remains intravenous until the requirement is met and the clinician considers switching appropriate.

A nurse injects the dedicated formulation into the abdomen. Hyaluronidase temporarily helps the medicine spread through the tissue for absorption. Two fixed rituximab doses are used in different treatment plans: 1,400 mg over approximately five minutes, or 1,600 mg over approximately seven minutes. The dose is not calculated from body surface area. The team chooses the correct strength and schedule.

The injection avoids bruised, tender, red, hard or scarred areas. You remain for at least 15 minutes afterwards, longer if your reaction risk warrants it. Premedication is still needed. A shorter injection does not mean that all reaction or infection risks have disappeared. These products must not be injected into a vein and are not routine self-injections.

Calendar, interruptions and handling

Treatment may be weekly for a short course, timed with other cancer treatment cycles, or spaced further apart during maintenance. Ask for your own calendar and planned review points rather than comparing appointment counts with another patient.

If an appointment is missed, contact the unit to rearrange it. Do not try to compensate with extra treatment. Vomiting does not remove medicine already given by infusion or injection, but persistent vomiting still needs assessment. There is no rituximab fasting requirement; follow any food instructions for other medicines or procedures.

The hospital pharmacy handles preparation, refrigerated storage and disposal. Do not transfer medicine between containers or store it at home unless the supplying service has given specific instructions. Report pain, burning, swelling or leakage around an intravenous line immediately.

Monitoring and checking whether treatment is working

The nurse checks your condition and vital signs during administration. Extra cardiac monitoring may be needed with a history of angina or abnormal rhythm, or if a rhythm problem develops. Tell staff about symptoms as soon as they begin, rather than waiting for the next observation.

Blood counts are checked before and during the course. The US intravenous label specifies counts before each monotherapy course and at weekly-to-monthly intervals with chemotherapy, more often if counts fall. Local schedules reflect the whole regimen. Low counts should be monitored after treatment until they recover.

Kidney function, blood salts and fluid balance need closer checks if tumour lysis is a concern. Hepatitis B monitoring follows the specialist plan during and after treatment. Recurrent or unusually prolonged infections may prompt immunoglobulin testing and an immunology assessment. Antibody replacement is appropriate for some patients, not everyone receiving rituximab.

Symptoms, examination, blood tests and scans help assess disease control. Treatment may be delayed for infection or low counts, slowed after a reaction, or discontinued after a serious complication. The subcutaneous product is not normally managed by simply reducing its fixed dose. These decisions depend on safety and the full regimen, not just how you feel on appointment day.

Common side effects and practical management

Reactions during or after administration

Fever, chills, itching, rash, nausea, headache, flushing or discomfort around tumour sites can occur, particularly during the first infusion. Tell the nurse immediately. Staff may pause treatment, give medicines and restart more slowly if safe. A reaction does not automatically mean treatment can never be used again, but severe reactions may require permanent discontinuation.

Reactions can occur after leaving, including within the first 24 hours. Use your urgent advice service for new symptoms; severe breathing problems or collapse require emergency care. Do not assume fever after treatment is simply an expected reaction, because infection may look similar.

Injection-site changes

Subcutaneous treatment can cause redness, itching, swelling, firmness or discomfort near the injection site. Some reactions begin more than 24 hours later. Inform the team and follow their skin-care advice. Rapidly spreading redness, worsening pain, fever or symptoms elsewhere need prompt assessment.

Tiredness, aches and headache

Rest when needed, but keep gently active within your limits. Ask before taking painkillers, particularly if platelets are low or kidney function is affected. A headache that is severe, persistent or accompanied by fever, confusion, neck stiffness or neurological changes needs urgent review.

Nausea, bowel and mouth symptoms

Small meals, regular drinks and prescribed anti-sickness medicines may help. Report persistent diarrhoea, vomiting or constipation. Severe abdominal pain or repeated vomiting must not be treated as a routine stomach upset. Gentle mouth care and a soft toothbrush can help if your regimen causes mouth soreness; contact the team if pain prevents drinking.

Low counts and infections

Low neutrophils, white cells that fight infection, can occur during treatment or weeks later. Low red cells may cause tiredness or breathlessness; low platelets may cause bruising or bleeding. Report these symptoms and attend blood tests even when you feel well. Chemotherapy given with rituximab can add substantially to these effects.

Hair thinning or loss can occur during treatment, and accompanying chemotherapy may be a major contributor. Ask about your actual treatment combination rather than assuming all listed effects will occur.

Less common but important side effects

Serious infections and delayed immune effects

Rituximab reduces B cells, and low antibody levels can persist after treatment. Bacterial, fungal and viral infections may become serious. Some treatment plans require preventive medicines against Pneumocystis pneumonia or herpes viruses. Take these for the prescribed duration, including after cancer treatment where advised. Not every patient needs the same preventive medicines.

Recent European information also warns about enteroviral meningoencephalitis, an infection involving the brain and its coverings. Persistent fever, severe headache, neck stiffness or confusion needs urgent assessment. Antibody-based infection tests can occasionally be falsely negative after B-cell-depleting treatment; tell any assessing clinician about rituximab, even months afterwards.

Hepatitis B reactivation

Reactivation can cause serious liver injury and may happen after treatment has ended. US information reports cases up to 24 months afterwards. Attend monitoring even without symptoms. Yellow skin or eyes, dark urine, unusual tiredness, vomiting or upper abdominal pain needs prompt medical advice. Positive past-infection tests must not be dismissed because a current surface-antigen result is negative. Reactivation requires immediate treatment withdrawal and specialist management.

Progressive multifocal leukoencephalopathy

PML is a rare, serious brain infection caused by reactivation of the JC virus. Seek urgent assessment for new or progressively worsening weakness, clumsiness, walking difficulty, changes in speech or vision, confusion, or personality changes. A relative may notice changes first. There can be other causes, but waiting for a routine appointment is unsafe. Sudden stroke-like symptoms are an emergency. Suspected PML requires withholding further doses during investigation; confirmed PML requires permanent discontinuation.

Tumour lysis syndrome

When many cancer cells break down quickly, their contents can disturb blood salts and harm the kidneys or heart. This is called tumour lysis syndrome and is particularly important early in treatment. Report reduced urine, repeated vomiting, muscle cramps, severe weakness, palpitations or confusion immediately. Preventive fluids and medicines reduce risk but do not replace monitoring. Follow your prescribed fluid plan, especially with heart or kidney disease.

Severe skin, heart, lung or bowel problems

Painful widespread rash, blisters, peeling skin or sores affecting the mouth, eyes or genitals can signal a serious skin reaction. Seek urgent care; extensive blistering or peeling is an emergency. Confirmed severe mucocutaneous reactions require treatment discontinuation; European instructions specify permanent withdrawal when a serious skin reaction is suspected to be related to treatment.

Chest pain, collapse, a new abnormal heartbeat or severe breathlessness can reflect a major reaction or heart or lung problem. Severe abdominal pain, swelling with repeated vomiting, or inability to pass stool or wind may indicate bowel obstruction or perforation, reported particularly with accompanying chemotherapy. These symptoms need immediate assessment.

Other medicines, supplements and vaccinations

Give the team a full medicine list, including steroids, immune-suppressing medicines, blood-pressure tablets, supplements and recent antibiotics. Other drugs can increase infection risk or complicate heart and kidney monitoring. Do not stop preventive antivirals or antibiotics without advice. Anticancer combinations are selected by the specialist; they should not be assembled from separate prescriptions yourself.

There is no standard grapefruit restriction or oral-tablet timing rule for rituximab itself. However, accompanying medicines may have food or enzyme interactions, so check the complete regimen.

Vaccines need planning because rituximab can greatly reduce the antibody response. Where possible, the US intravenous prescribing information advises non-live vaccines at least four weeks before a course. This does not mean urgently needed cancer treatment should be delayed by the patient. The team decides timing and whether a vaccine should be repeated later.

Do not receive a live vaccine without specialist advice during treatment or while immune function remains impaired afterwards. Non-live vaccines, including injectable influenza and COVID-19 vaccines, may still be recommended, although protection can be lower. There is no single recovery date that makes every vaccine suitable. Discuss travel vaccines well in advance.

Everyday life during treatment

Wash hands regularly, practise food hygiene and avoid close contact with people who are clearly unwell. Report repeated respiratory infections or prolonged fever rather than repeatedly treating them at home. You do not usually need to avoid all social contact; precautions should reflect your counts and treatment plan.

Protect against mosquito and tick bites with suitable repellent, covering clothing and screens or nets where appropriate. Current CDC guidance highlights a risk of unusually severe infections transmitted by these insects after B-cell-depleting treatment. Tell the team about relevant travel, bites and any subsequent fever or neurological symptoms.

Arrange transport after the first treatment, since antihistamines may make you sleepy. Do not drive when drowsy, dizzy or unwell. Plan work, exercise and travel around recovery, appointments and access to urgent care. Maintain nutrition and fluids within any prescribed restrictions. Tell dentists about rituximab before procedures.

Ask for help with fatigue, financial or practical difficulties, sexual concerns and anxiety. Maintenance treatment can feel emotionally different from a short course; support remains appropriate even when appointments are spaced out.

Fertility, contraception, pregnancy and breastfeeding

Rituximab can affect a developing baby's B cells. Pregnancy testing is recommended before treatment if you could become pregnant. Use effective contraception during treatment and for 12 months after the last rituximab dose. This interval applies to both intravenous and subcutaneous treatment. Report a suspected pregnancy promptly so specialists can discuss treatment and infant monitoring.

Current rituximab labels do not specify a separate fixed male contraception interval. Other medicines, especially chemotherapy, may impose precautions for patients and partners. Obtain a written plan for the whole regimen rather than borrowing the interval for a different drug.

Rituximab's effect on human fertility is not fully established. Accompanying treatments may reduce fertility. Discuss sperm, egg or embryo preservation before treatment where relevant; absence of periods does not reliably prevent pregnancy.

US product information advises no breastfeeding during treatment and for six months after the last dose. European professional information says breastfeeding is not recommended during treatment and optimally for six months afterwards; its patient leaflet also advises six months. Small amounts enter breast milk, but this does not establish long-term infant safety. Follow the specialist plan and any longer restriction required by accompanying medicines.

After treatment finishes

Keep attending follow-up and any blood-count, immunoglobulin or hepatitis B checks. Low white cells, low antibodies and infection risk can continue or appear later. Continue preventive medicines until the team gives a stopping date, not simply until the last infusion.

Keep a record of the product and last treatment date for future clinicians. Vaccinations, new immune-suppressing medicines and pregnancy planning may need that information. A normal blood count does not necessarily mean every aspect of immune protection has recovered. Contact the team about recurrent infections, neurological changes or other concerning symptoms rather than waiting for scheduled follow-up.

Frequently asked questions