Contact your doctor if any of these side effects persists or are bothersome:

• Diarrhea
• Nausea
• Stomach (abdominal) pain
• Common cold
• Runny nose
• Upper respiratory tract infection
• Changes in the type of bacteria in your sputum
• Headache
• Dizziness
• Nasal congestion
• Sinus congestion
• Sore throat
• Rash
• Joint pain

Various mutations of the cystic fibrosis gene block the "gates" that allow the flow of salt across the cell membranes. This causes mucus to become thick and clog the lungs. Ivacaftor is a "cystic fibrosis transmembrane conductance regulator (CFTC) potentiator". The CFTR protein is a channel at the surface of the cells that allows the movement of particles such as chloride in and out of the cell, contributing to salt and water balance. Ivacaftor helps this CFTR protein channel or "open the gates" more often allowing more salt to pass through.  The thick mucus is reduced and cystic fibrosis symptoms lessen. 

Use with caution if you:

• have kidney or liver problems
• have cataracts

Possible drug interactions: 

• ketoconazole, itraconazole, posaconazole, voriconazole, fluconazole​
• some antibiotics such as clarithromycin, erythromycin, rifampin, rifabutin
• phenobarbital, carbamazepine, phenytoin 
• midazolam, alprazolam, diazepam, triazolam 
• digoxin
• cyclosporine, tacrolimus 
• warfarin 
• St. John’s wort 

Use in pregnancy and breastfeeding.  Little is known about the safety of this medication when used in pregnancy and breastfeeding.  Consult your doctor or pharmacist before use.