Natalizumab
Side effects
Because natalizumab is a relatively new treatment, information on the possible long term effects of treatment is still emerging, and it can be difficult to estimate how likely patients are to have these effects. However, a number of important side effects have been reported with patients on natalizumab.
Allergic reactions (also called 'hypersensitivity reactions') are a reaction to the medicine or any of the ingredients used to prepare the medicine. They affect around 1 in 25 people who take natalizumab.
Symptoms of an allergic reaction include itchy rash (hives), swelling of face, lips or tongue, difficulty breathing. These may be accompanied by a change in vital signs (decreased blood pressure, increased temperature, increase in pulse rate or heart rate and difficulty breathing). Allergic reactions can occur during the infusion or within an hour of completing the infusion.
If you experience an allergic reaction to natalizumab, your treatment will need to be stopped immediately
and you will need medical attention. If the allergy is confirmed, you will not be able to have any
more treatment with natalizumab.
Natalizumab may increase your chance of getting an unusual or serious infection because it can affect your immune system.
This is a rare but very serious brain infection which usually causes death or severe disability. There is no known treatment, prevention or cure for PML. PML usually happens in people with weakened immune systems, and so your chances of getting it may be higher if you are also being treated with other medicines that can weaken your immune system.
Based on the number of PML cases reported to date, the risk of developing PML is thought to be around 1 in 1000. However, the risk of developing PML appears to increase after two years of treatment. In view of this increased risk, the patient information leaflet states that people should be re-informed about the increased risk of PML after 2 years and continuation of treatment only considered after a reassessment of the benefits versus the risks of treatment.
Because of the risk of PML, all hospitals which prescribe natalizumab have 'clinical vigilance' programmes to make sure that both healthcare professionals and patients are aware of the risks, know what to look out for and take the right action if they notice any signs of PML. If you are taking natalizumab you will have to carry a patient alert card with you. The patient alert card describes the symptoms of PML and stresses the importance of contacting a health professional if you experience any of these symptoms.
Some patients taking natalizumab have experienced severe liver problems although this is rare, affecting less than 1 in 1,000 people. Signs of possible liver problems include yellowing of your skin or the whites of your eyes and unusual darkening of the urine.
