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Hicon Side Effects

Generic name: sodium iodide-i-131

Medically reviewed by Last updated on Apr 12, 2021.

Note: This document contains side effect information about sodium iodide-i-131. Some of the dosage forms listed on this page may not apply to the brand name Hicon.

For the Consumer

Applies to sodium iodide-i-131: oral kit

Side effects requiring immediate medical attention

Along with its needed effects, sodium iodide-i-131 (the active ingredient contained in Hicon) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking sodium iodide-i-131:

After treatment of overactive thyroid

Symptoms of an underactive thyroid

  • Changes in menstrual periods
  • clumsiness
  • coldness
  • drowsiness
  • dry, puffy skin
  • headache
  • listlessness
  • muscle aches
  • thinning of the hair (temporary)
  • unusual tiredness or weakness
  • weight gain


After treatment of overactive thyroid

  • Excessive sweating
  • fast, irregular, pounding, or racing heartbeat or pulse
  • fever
  • unusual irritability

After treatment of cancer of the thyroid

  • Black, tarry stools
  • blood in the urine or stools
  • cough or hoarseness
  • fever or chills
  • lower back or side pain
  • painful or difficult swallowing
  • painful or difficult urination
  • pinpoint red spots on the skin
  • unusual bleeding or bruising

Incidence not known

After treatment of overactive thyroid

  • Chest pain
  • fast, pounding, or irregular heartbeat or pulse
  • hives, itching, and rash
  • nervousness
  • sensitivity to heat
  • sweating
  • tenderness of salivary glands
  • trouble sleeping
  • weight loss

After treatment of cancer of the thyroid

  • Abdominal or stomach cramps
  • bleeding gums
  • bone pain
  • diarrhea
  • feeling of discomfort
  • loss of appetite
  • nausea
  • sore throat
  • unusual tiredness or weakness
  • vomiting
  • weakness

Side effects not requiring immediate medical attention

Some side effects of sodium iodide-i-131 may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

After treatment of overactive thyroid or cancer of the thyroid

  • Neck tenderness or swelling
  • sore throat

After treatment of cancer of the thyroid

For Healthcare Professionals

Applies to sodium iodide-i-131: compounding powder, oral capsule, oral liquid


Cardiovascular side effects have included chest pain and tachycardia.[Ref]


Dermatologic side effects have included itching skin, rash, and hives.[Ref]


Endocrine side effects have included acute thyroid crisis.[Ref]


Gastrointestinal side effects have included nausea and vomiting.[Ref]


Hematologic side effects have included blood dyscrasia, leukopenia, thrombocytopenia, depression of hematopoietic system, and anemia.[Ref]


Local side effects have included tenderness and swelling of the neck, pain on swallowing, sore throat, and cough (usually around the third day after treatment).[Ref]


Oncologic side effects have included acute leukemia.[Ref]


Other side effects have included temporary thinning of the hair (may occur 2 to 3 months after treatment), chromosomal abnormalities, radiation sickness, and death.[Ref]


1. Saha GB. "Fundamentals of Nuclear Pharmacy. 4th ed." New York, NY: Springer-Verlag (1998):

2. "Product Information. Sodium Iodide-1-131 (sodium iodide-I-131)." Mallinckrodt Medical Inc, St. Louis, MO.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.