Get emergency medical help if you have signs of an allergic reaction to Tysabri: hives, rash; wheezing, difficult breathing; swelling of your face, lips, tongue, or throat.
Some allergic reactions may occur during the injection. Tell your caregiver right away if you feel dizzy, nauseated, light-headed, itchy, cold, sweaty, or if you have chest pain, trouble breathing, or swelling in your face.
Tysabri may cause serious viral infections of the brain or spinal cord that can lead to disability or death. Call your doctor right away if you have any of the following symptoms during treatment with Tysabri or up to 6 months after your last dose (these symptoms may start gradually and get worse quickly):
sudden fever or severe headache;
confusion, memory problems, or other changes in your mental state;
weakness on one side of your body;
vision changes, eye pain or redness;
problems with speech or walking; or
trouble using your arms and legs.
Also call your doctor at once if you have:
fever, chills, cough with yellow or green mucus;
easy bruising, unusual bleeding (nosebleeds, bleeding gums, heavy menstrual periods), purple or red spots under your skin;
any bleeding that will not stop;
pain or burning when you urinate; or
liver problems - nausea, upper stomach pain, itching, tiredness, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).
Common Tysabri side effects may include:
headache, tired feeling;
nausea, diarrhea, stomach pain;
cold symptoms such as stuffy nose, sneezing, sore throat;
joint pain, pain in your arms and legs; or
vaginal itching or discharge.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Tysabri side effects (more detail)
