Rituximab (Riximyo)
Riximyo (rituximab) is a biologic medicine that treats the pain and swelling of arthritis by suppressing part of the body’s immune system.
Riximyo destroys a type of white blood cell that has a role in the body’s immune system called the B-cell.
Riximyo can help in the treatment of a wide variety of diseases including rheumatoid arthritis and other autoimmune diseases, some types of cancer, and ultimately any disease that involves unwanted activity from B-cells. Riximyo is also used to help prevent tissue rejection in organ transplant patients.
Biosimilar
Riximyo is a type of medicine that is called a biosimilar. A biosimilar is a type of biologic medication that is designed to be identical to an existing biologic medication, but is created using a different process.
Riximyo is a biosimilar of Rituxan. Both medications are known by the same generic name: rituximab. Biosimilars are usually available at a lower price than the original medication.
Taking Riximyo
Riximyo is available as an intravenous (IV) infusion.
Some patients feel better soon after receiving the medication, but in others, it can take longer: up to 3 or 4 months.
The normal dose is 1000 mg in each infusion. A steroid called methylprednisolone (Solumedrol) is usually given 30 minutes before the Riximyo infusion to help prevent reactions to it.
For rheumatoid arthritis, when starting Riximyo, the first dose is given on week 0. The second dose is given two weeks later. This cycle may be repeated again any time after 6 months depending on the patients’ response.
For vasculitis, when starting Riximyo, doses are given each week for four (4) weeks in a row. Subsequent doses can be given according to the clinical response to the medication.
Important Tests and Risks
All patients should have hepatitis B testing done before starting Riximyo.
In patients who have had hepatitis B or are a carrier of hepatitis B, Riximyo risks causing the virus to become an active infection again.
Regular blood tests are not normally required for people who take Riximyo. However, doctors treating arthritis will likely order occasional blood tests to monitor their patient’s blood counts and follow the activity of the disease.
Science
In some people with inflammatory arthritis, the cells of the immune system become confused. They mistake the cells of the body’s own joints for foreign invaders and decide to “attack” them. Arthritis that is caused by this activity may be called an autoimmune disease.
The B-cell is a type white blood cell that forms part of the body’s immune system. It is partly responsible for this attack on the joints.
Riximyo is a specially-designed protein called a monoclonal antibody that targets a specific protein found on the surface of B-cells called CD20. When Riximyo binds to the surface of a B-cell, it causes their destruction.
By deleting B-cells from the body, Riximyo works to suppress a part of the body’s immune system. Although this suppression may make it slightly harder for patients to fight off infections, it also helps to stabilize an overactive immune system.
Safety
Some side effects or reactions may occur for some patients during or shortly after the infusion.
Patients who take Riximyo can very rarely develop a serious brain infection. Patients should call a doctor immediately if they experience changes in mental state, decreased vision, or problems with speech or walking. These symptoms may start gradually and get worse quickly.
MORE COMMON side-effects include:
- Abdominal pain, nausea, and diarrhea
- Sore muscles or joints
- Rash, hives, or itchiness
- Headaches, dizziness, or tingling
- Sore throat, fever, chills, & general weakness
- Increase in blood pressure
RARE side-effects include:
- Infusion Reaction – Many patients will react to the medication during or shortly after the infusion, most likely during the first infusion and less so with future infusions. Most of these reactions are not severe.
- Infection – As is the case with many medications used in the treatment of arthritis there is an increased risk of serious infections associated with the use of Riximyo. Any infections or fevers should be taken very seriously and reviewed by a doctor.
- Rare brain infection – Patients have very rarely developed a rare brain infection called Progressive Multifocal Leukoencephalopathy while taking Riximyo.
- Skin – Severe skin reactions have been reported with Riximyo .
- Heart – Riximyo has been associated with abnormal heart rhythms. Patients who have known heart rhythm problems should discuss them with their doctor to understand the potential impact of this medication.
- Blood Counts – Riximyo can cause a drop in the numbers of white blood cells (which are needed to fight infection) or red blood cells (which carry oxygen). This is very rare and it is unusual for this to be a serious problem.
People who should NOT take Riximyo include:
- Those who have had a previous serious allergic reaction to Riximyo
- Women who are pregnant, planning on becoming pregnant, or breast feeding
- Patients with active infections (such as tuberculosis or hepatitis B)
- Patients with a history of hepatitis B or are carriers of the disease
Patients should call their doctor if they feel sick and want to stop, or they are concerned about any side effects.
Other reasons to call a doctor while taking Riximyo include:
- Fever or possible infection
- If another doctor has prescribed antibiotics to fight an infection
- Before having surgery
- Pregnancy or planning on becoming pregnant
- Planning to get any vaccinations
- Rash
Anyone who becomes pregnant while taking Riximyo should notify their doctor immediately.
Pregnancy and medicationsVideo
Watch Canadian rheumatologist Dr. Andy Thompson introduce Riximyo.
Resources
DIN
- 02498316 (IV)