Why the Same Drug Treats — Arthritis and Lymphoma

No. Rituximab is used in both conditions because both involve overactive or abnormal B cells. Being prescribed it for arthritis means your rheumatologist has decided that a medicine targeting B cells is the right approach for your level of disease activity. It does not mean you have cancer or are being treated like a cancer patient. The dose and schedule for autoimmune disease are different from those used in lymphoma.

Rituximab is given as a day-care infusion — you do not usually need to stay overnight. At CION, biological therapy infusions are administered as day care across our centres. You are monitored throughout the drip and can go home the same day if you tolerate it well. The first infusion is given slowly because infusion reactions are most common during that session. Later infusions may be given more quickly if the first was straightforward. Your team will confirm the timing in advance.

The most common side effect during treatment is an infusion reaction — fever, chills, or a drop in blood pressure while the drip is running. This is why the first session is given slowly and you are monitored throughout. After treatment, your B cell count is reduced, which lowers your ability to make new antibodies and raises your risk of certain infections. Tell your team about any signs of infection promptly rather than waiting for your next scheduled visit.

Yes, to a degree. Rituximab depletes all B cells carrying CD20 — including healthy ones — because it cannot tell them apart from the abnormal ones. B cells are responsible for making the antibodies that protect you from many infections. While your B cell count is reduced, which can take months to recover, you are more vulnerable to certain bacterial and viral infections. Your team will monitor your immunoglobulin levels with regular blood tests and may discuss supplements if levels fall significantly.

Live vaccines — such as MMR or varicella — should not be given while your B cells are depleted. Rituximab prevents you from mounting a proper immune response to live vaccines, and there is a small risk that a live vaccine could cause infection in this setting. Inactivated vaccines are generally safer, but timing matters. EULAR guidance recommends completing recommended vaccinations before starting rituximab if possible. Ask your specialist which vaccines you are due and when the right time is to have them.

In autoimmune disease, the response usually develops over weeks to months. B cells are depleted relatively quickly after the infusion, but the reduction in inflammation and improvement in symptoms follows more slowly. Your rheumatologist will reassess you at follow-up appointments to judge the response. In lymphoma, response is assessed with imaging — such as a PET-CT scan coordinated through a partner imaging centre — after a set number of treatment cycles, as planned by your oncologist.