Tell your doctor immediately if any of these unlikely but serious side effects occur:
- severe headache
- fast/pounding heartbeat
- signs of infection (such as fever, persistent sore throat, breathing problems, unusual vaginal discharge, painful/frequent urination)
- mood changes (such as depression, suicidal thoughts)
- severe stomach/abdominal pain
This drug increases the risk of a possibly fatal brain infection (see Warning section for more details). In MS patients, the symptoms of PML can seem like an attack of worsening MS. Therefore, whether you are using this drug for MS or CD, tell your doctor immediately of any worsening symptoms that persist for several days such as:
- clumsiness
- sudden change in your thinking (such as confusion, difficulty concentrating)
- difficulty moving muscles
- seizure
- problems with speech
- vision changes
This drug may rarely cause serious liver problems. If you notice any of the following rare but very serious side effects, tell your doctor immediately:
- persistent nausea/vomiting
- dark urine
- yellowing eyes/skin
- feeling tired/weak
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms:
- rash
- itching/swelling (especially of the face/tongue/throat)
- severe dizziness
- trouble breathing
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
Call your doctor for medical advice about side effects. In the US, you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088.
In Canada, you may report side effects to Health Canada at 1-866-234-2345.
TYSABRI IV Medical Alert
Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).
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