Potassium iodide is used to loosen and break up mucus in the airways. This helps you cough up the mucus so you can breathe more easily if you have long-term lung problems (such as asthma, chronic bronchitis, emphysema). This medication is known as an expectorant.

Potassium iodide is also used along with antithyroid medicines to prepare the thyroid gland for surgical removal, to treat certain overactive thyroid conditions (hyperthyroidism), and to protect the thyroid in a radiation exposure emergency. It works by shrinking the size of the thyroid gland and decreasing the amount of thyroid hormones produced.

In a radiation emergency, potassium iodide blocks only the thyroid from absorbing radioactive iodine, protecting it from damage and reducing the risk of thyroid cancer. Use this medication along with other emergency measures that will be recommended to you by public health and safety officials (such as finding safe shelter, evacuation, controlling food supply).

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used for a certain type of fungal skin infection (sporotrichosis).

Take this medication by mouth with a full glass of water (8 ounces or 240 milliliters) as directed by your doctor or public health and safety officials. To avoid stomach upset, take after meals or with food. Drink plenty of liquids with this medication unless otherwise directed. If you are taking the tablets, do not lie down for at least 10 minutes after taking this medication. If you are using the drops or liquid medication, use the dropper that comes with the bottle or a medication spoon/device to measure the correct dose. Liquid forms of this product may be mixed in water, milk, formula, or juice before taking. Do not use this medication if the solution turns brownish-yellow.

The dosage is based on your medical condition and response to treatment. Children's dosage is also based on age. Do not increase your dose, take it more often, or take it for longer than prescribed or recommended because of the increased risk of side effects.

In a radiation emergency, take this drug only when public health and safety officials tell you to do so. Read the Patient Information Leaflet that comes with the medication. Start treatment as soon as possible for the best protection. Take this medication usually once every 24 hours. The length of treatment will be determined by public health and safety officials and depends on several factors (such as whether you continue to be exposed to the radiation, and whether you are pregnant, breastfeeding, or have a newborn baby). See also Precautions.

If so directed, use this medication regularly to get the most benefit from it. To help you remember, take it at the same time(s) each day.

Tell your doctor if your condition lasts or gets worse.

Nausea, vomiting, stomach ache, diarrhea, metallic taste in the mouth, fever, headache, or acne may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

If your doctor has directed you to use this medication, remember that your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• burning mouth/throat
• sore teeth/gums
• swelling inside the mouth
• increased saliva
• eye irritation/swollen eyelids
• severe headache
• swelling of the front of the neck/throat (goiter)
• signs of decreased thyroid gland function (such as weight gain, cold intolerance, slow/irregular heartbeat, constipation, unusual tiredness)
• confusion
• numbness/tingling/pain/weakness of the hands/feet

Get medical help right away if you have any very serious side effects, including:

• chest pain
• black stools
• vomit that looks like coffee grounds
• bloody diarrhea

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing
• fever with joint pain

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking potassium iodide, tell your doctor or pharmacist if you are allergic to it; or to iodine; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• current attack/worsening of bronchitis (if taking potassium iodide to thin mucus in the lungs)
• a certain type of skin condition (dermatitis herpetiformis)
• a certain type of blood vessel disease (hypocomplementemic vasculitis)
• certain thyroid disorders (such as multinodular goiter, Graves' disease, autoimmune thyroiditis, nodular thyroid disease with heart disease)
• overactive thyroid disease (unless you are specifically prescribed potassium iodide to treat hyperthyroidism)
• tuberculosis
• high potassium blood level
• kidney disease
• Addison's disease
• a certain muscle disorder (myotonia congenita)

Caution is advised when this drug is given to newborn babies younger than 1 month old. Treatment for more than 1 day should be avoided because repeated dosing increases the risk of blocking thyroid function, possibly affecting the newborn's brain development. If treatment is needed for longer than 1 day, discuss the risks and benefits with the doctor. Treated babies should be given thyroid function tests.

During pregnancy, this medication should be used only when clearly needed. Treatment for more than 1 day should be avoided because repeated dosing increases the risk of blocking thyroid function in the unborn baby, possibly causing harm. If treatment is needed for longer than 1 day, discuss the risks and benefits with your doctor.

Caution is advised when this drug is used by women who are breastfeeding. This drug passes into breast milk. Treatment for more than 1 day should be avoided if you are breastfeeding because repeated dosing increases the risk of blocking thyroid function in the nursing infant. This effect may cause harm, especially in newborns younger than 1 month old. If treatment is needed for longer than 1 day, discuss with your doctor the risks and benefits, as well as whether you should stop breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are:

• ACE inhibitors (such as captopril, lisinopril)
• angiotensin receptor blockers (ARBs such as losartan, valsartan)
• certain "water pills" (potassium-sparing diuretics such as amiloride, spironolactone, triamterene)
• drospirenone
• eplerenone
• lithium
• potassium-containing drugs (including supplements such as potassium chloride)

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as thyroid function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not freeze. If crystals form in the solution, dissolve them by placing the closed bottle in a container of warm water, then gently shake the bottle. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.