Sodium iodide I 131 (By mouth)


Sodium Iodide I 131 (SOE-dee-um EYE-oh-dide I 131)

Treats an overactive thyroid and thyroid cancer. This medicine is a radioactive substance.

Brand Name(s)

There may be other brand names for this medicine.

When This Medicine Should Not Be Used

You should not receive this medicine if you have had an allergic reaction to sodium iodide I 131, or if you are pregnant or have nausea or vomiting.

How to Use This Medicine


  • Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
  • A nurse or other trained health professional will give you this medicine in a hospital or clinic.
  • Your doctor may have instructions for you to get ready for your treatment. Check with your doctor ahead of time if you have not received instructions or you do not understand them.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows about all thyroid medicine you use (such as thyroxine, liothyronine, Levoxyl®, Synthroid®) as well as any anti-thyroid medicine (such as carbimazole, propylthiouracil).
  • Also tell your doctor about anything else you have used that might contain iodine, or if you have had any medical tests (such as a CT scan) that included a contrast agent. Iodine could be found in amiodarone (Coradone®), lithium (Eskalith®, Lithobid®), tolbutamide (Orinase®), steroids (such as dexamethasone, Medrol®), blood thinners (such as warfarin, Coumadin®), vitamins, cough medicine, allergy medicine, sulfa drugs (trimethoprim, Bactrim®, Cotrim®, Septra®), skin cleansers, or antiseptics (such as povidone).

Warnings While Using This Medicine

  • Use of this medicine while you are pregnant can harm your unborn baby. Women may receive a pregnancy test before they receive this medicine to make sure they are not pregnant.
  • Use 2 forms of birth control to avoid pregnancy while you are using this medicine. Keep using 2 forms for at least 6 months after your treatment ends. This is very important for both men and women. You might need to use extra birth control for a longer time if you need more therapy. If a pregnancy occurs while you are using this medicine, tell your doctor right away.
  • Tell your doctor if you are breastfeeding. You will need to stop breastfeeding or breast pumping for at least 4 weeks before you receive this medicine.
  • Make sure your doctor knows if you have kidney disease, heart disease, asthma, neck or throat problems, or a history of sulfite allergy.
  • This medicine may increase your risk for cancer or thyroid problems. Talk with your doctor about these risks. You may need to take other medicine with this medicine to prevent thyroid problems.
  • You will be exposed to dangers of radiation while using this medicine. Talk with your doctor about precautions that you should take for yourself and for the people around you.
  • This medicine might cause temporary infertility in both men and women. Discuss this with your doctor if you plan to have children.
  • This medicine lowers the number of some types of blood cells in your body. Because of this, you may bleed or get infections more easily. To help with these problems, avoid being near people who are sick or have infections. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.
  • Your doctor will need to check your blood or urine at regular visits while you are using this medicine. Be sure to keep all appointments.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Chest pain
  • Choking, coughing, trouble swallowing
  • Fast heartbeat
  • Fever, extreme weakness, very fast heartbeat, confusion
  • Pain when swallowing
  • Painful, dry, burning, watery, itchy eyes or mouth
  • Sore or swollen neck or throat
  • Unusual bleeding or bruising

If you notice these less serious side effects, talk with your doctor:

  • Cough, mild sore throat
  • Mild nausea or vomiting

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last Reviewed on 06/12/2013

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