Iobenguane I-123 is in a group of drugs called diagnostic radiopharmaceuticals (RAY dee oh far ma SOO tik als). Iobenguane I-123 is a radioactive agent that allows images of specific organs in the body to be detected by a gamma camera.

Iobenguane I-123 is used to detect certain kinds of tumors.

Iobenguane I-123 is also used in people with congestive heart failure to assess the function of nerves that control the heart muscle. Iobenguane I-123 can detect nerve damage to help identify a patient's risk of death from heart failure.

Iobenguane I-123 may also be used for purposes not listed in this medication guide.

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Iobenguane I-123 is injected into a vein through an IV. You will receive this injection in a clinic or hospital setting. It is usually given about 24 hours before your radiologic test.

At least 1 hour before you are treated with iobenguane I-123, you may be given a liquid drink that contains medicine to protect your thyroid from harmful radioactive effects of iobenguane I-123.

Drink extra fluids before you receive iobenguane I-123, and for at least 48 hours afterward. Follow your doctor's instructions about the types and amount of liquids you should drink before and after your test. Iobenguane I-123 is radioactive and it can cause dangerous effects on your bladder if it is not properly eliminated from your body through urination.

Expect to urinate often during the first 48 hours after your test. You will know you are getting enough extra fluid if you are urinating more than usual during this time. Urinating often will help rid your body of the radioactive iodine.

You should not be treated with iobenguane I-123 if you are allergic to iobenguane or iobenguane sulfate.

Tell your doctor if you have ever had:

• kidney disease;

• a thyroid disorder;

• Parkinson's disease or other neurologic disorder;

• high blood pressure;

• if you are dehydrated or unable to urinate; or

• if you are allergic to iodine.

Older adults may need kidney function tests before receiving iobenguane I-123. Your kidney function may also need to be watched closely after you have received this medication.

It is not known whether iobenguane I-123 will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant. There is a potential risk of fetal exposure to radiation while using iobenguane I-123.

It is not known whether iobenguane I-123 passes into breast milk or if it could harm a nursing baby. You should not breastfeed for at least 6 days after receiving iobenguane I-123. If you use a breast pump during this time, throw out any milk you collect. Do not feed it to your baby.

Since iobenguane I-123 is given only once before your radiologic test, you will not be on a dosing schedule.

Call your doctor if for some reason you will not be able to complete your radiologic test within 24 hours after you receive your injection.

Since this medication is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

Do not allow yourself to become dehydrated during the first few days after receiving iobenguane I-123. Call your doctor if you have any vomiting or diarrhea during this time. Follow your doctor's instructions about the types and amount of fluids you should drink.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Common side effects of iobenguane I-123 may include:

• dizziness;

• rash, itching;

• flushing (warmth, redness, or tingly feeling);

• headache; or

• bleeding around your IV needle.

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.

Some medicines can interfere with the quality of images produced by iobenguane I-123. Tell your doctor about all your current medicines and any you recently stopped using, especially:

• an antidepressant such as amitriptyline, bupropion, citalopram, desipramine, fluoxetine, imipramine, paroxetine, sertraline, Wellbutrin, Zoloft, Prozac, Celexa, and others;

• blood pressure medication; or

• cough, cold, or allergy medicine that contains a decongestant (phenylephrine or pseudoephedrine).

This list is not complete. Other drugs may interact with iobenguane I-123, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.