Ivacaftor and tezacaftor is a combination medicine used to treat cystic fibrosis in adults and children who are at least 6 years old.

Ivacaftor and tezacaftor is for use only in patients with a specific gene mutation related to cystic fibrosis. Before you take ivacaftor and tezacaftor, you may need a medical test to make sure you have this gene mutation.

Ivacaftor and tezacaftor may also be used for purposes not listed in this medication guide.

Tell your doctor about all your current medicines and any you start or stop using. Many drugs can interact, and some drugs should not be used together.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Ivacaftor and tezacaftor is supplied as two separate daily tablets. A yellow tablet is taken in the morning and a blue tablet is taken 12 hours later. Follow your doctor's dosing instructions very carefully.

Always take this medicine with food that contains fat, such as butter, peanut butter, whole milk, cheese, yogurt, or cheese pizza. Follow your doctor's dosing instructions very carefully.

You will need frequent blood tests to check your liver function. Your blood pressure may also need to be checked often.

A child using this medicine may need frequent eye exams to check for cataracts.

Store at room temperature away from moisture and heat. Keep each tablet in its daily blister strip until you are ready to take your dose.

You should not use ivacaftor and tezacaftor if you are allergic to ivacaftor or tezacaftor.

Some medicines can cause unwanted or dangerous effects when used with ivacaftor and tezacaftor. Your doctor may change your treatment plan if you also use:

• St. John's wort;

• seizure medicine--carbamazepine, phenobarbital, phenytoin; or

• tuberculosis medicine--rifabutin, rifampin.

Tell your doctor if you have ever had:

• liver disease; or

• kidney disease.

Tell your doctor if you are pregnant or breastfeeding.

Ivacaftor and tezacaftor is not approved for use by anyone younger than 6 years old.

Take the medicine as soon as you can, but skip the missed dose if you are more than 6 hours late for the dose. Do not take two doses at one time.

Be sure to take a missed dose with a food that contains fat.

If you miss doses or stop taking ivacaftor and tezacaftor for more than 1 week, call your doctor before you start taking the medicine again. You may need a different dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Avoid driving or hazardous activity until you know how ivacaftor and tezacaftor will affect you. Your reactions could be impaired.

Grapefruit and Seville oranges may interact with ivacaftor and tezacaftor and lead to unwanted side effects. Avoid the use of grapefruit products and orange marmalades.

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

Ivacaftor and tezacaftor may cause serious side effects. Call your doctor at once if you have:

• vision problems; or

• liver problems--loss of appetite, stomach pain (upper right side), dark urine, jaundice (yellowing of the skin or eyes).

Common side effects of ivacaftor and tezacaftor may include:

• stuffy nose;

• dizziness;

• nausea; or

• headache.

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.

Your doctor may adjust your ivacaftor and tezacaftor dose if you also use other medicines, especially:

• an antibiotic--clarithromycin, erythromycin, telithromycin; or

• antifungal medicine--fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole.

This list is not complete. Other drugs may affect ivacaftor and tezacaftor, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.