This medication is used to treat cystic fibrosis in certain people (those with an abnormal "CFTR" gene). It may help to improve breathing, reduce the risk of lung infections, and improve weight gain.

Read the Patient Information Leaflet if available from your pharmacist before you start taking ivacaftor and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth as directed by your doctor, usually twice daily (every 12 hours).

If you are taking the tablet form of this medication, take this medication with fat-containing foods (such as eggs, butter, peanut butter, cheese). The manufacturer directs to swallow this medication whole. However, many similar drugs (immediate-release tablets) can be split/crushed. Follow your doctor's directions on how to take this medication.

If you are taking the granules form of this medication, gently shake the packet before use. Empty the packet into a small cup with 1 teaspoonful (5 milliliters) of soft food (such as yogurt, applesauce) or liquid (such as water, milk, infant formula). The soft food or liquid should be at or below room temperature. Mix the granules with the soft food or liquid and take the entire mixture within 1 hour of mixing. Eat a fat-containing food either right before or just after taking the mixture.

The dosage is based on your medical condition, age, weight, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

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

Avoid eating grapefruit or drinking grapefruit juice while using this medication unless your doctor or pharmacist says you may do so safely. Grapefruit can increase the chance of side effects with this medicine. Ask your doctor or pharmacist for more details.

Tell your doctor if your condition does not get better or if it gets worse.

Dizziness, headache, or nausea may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because 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:

• vision changes

Ivacaftor may rarely cause serious liver disease. Get medical help right away if you have any symptoms of liver damage, including:

• nausea/vomiting that doesn't stop
• loss of appetite
• dark urine
• stomach/abdominal pain
• yellowing eyes/skin

Ivacaftor can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Tell your doctor right away if you develop any rash.

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

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 ivacaftor, tell your doctor or pharmacist if you are allergic to it; 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:

• liver disease

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. Consult your doctor before breastfeeding.

See also How To Use section.

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.

Other medications can affect the removal of ivacaftor from your body, which may affect how ivacaftor works. Examples include mifepristone, rifamycins (such as rifabutin), drugs for seizures (such as carbamazepine, phenytoin), St. John's wort, among others.

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 CFTR gene testing, liver/lung function, eye exams) will be done before you start taking this medication and while you are taking it. 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 more than 6 hours after the missed 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 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.