What the label lists and what reports show
Ivacaftor side effects
Ivacaftor's FDA label: “The most common adverse drug reactions to KALYDECO (≥8% of patients with CF who have a G551D mutation in the CFTR gene) were headache, oropharyngeal pain, upper respiratory tract infection, nasal congestion, abdominal pain, nasopharyngitis, diarrhea, rash …” FAERS holds 7,897 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is infective pulmonary exacerbation of cystic fibrosis (610 reports).
- No generic listed
Check it at the source: the ivacaftor FDA label on DailyMed (effective March 23, 2026, Vertex Pharmaceuticals Incorporated); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of KALYDECO?KALYDECO can cause serious side effects, including: High liver enzymes in the blood, which have happened in people receiving KALYDECO. Your doctor will do blood tests to check your liver: before you start KALYDECO every 3 months during your first year of taking KALYDECO every year while you are taking KALYDECO For people who have had high liver enzymes in the past, your doctor may do blood tests to check the liver more often. Call your doctor right away if you have any of the following symptoms of liver problems: pain or discomfort in the upper right stomach (abdominal) area yellowing of your skin or the white part of your eyes loss of appetite nausea or vomiting dark, amber-colored urine Serious Allergic Reactions can happen to people who are treated with KALYDECO. Call your healthcare provider or go to the emergency room right away if you have any symptoms of an allergic reaction. […]
Source: FDA drug label, Vertex Pharmaceuticals Incorporated, effective March 23, 2026 (SPL set 0ab0c9f8-3eee-4e0f-9f3f-c1e16aaffe25), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse drug reactions to KALYDECO (≥8% of patients with CF who have a G551D mutation in the CFTR gene) were headache, oropharyngeal pain, upper respiratory tract infection, nasal congestion, abdominal pain, nasopharyngitis, diarrhea, rash, nausea, and dizziness.
Table 2: Incidence of Adverse Drug Reactions in ≥8% of KALYDECO-Treated Patients with a G551D Mutation in the CFTR Gene and Greater than Placebo in 2 Placebo-Controlled Phase 3 Clinical Trials of 48 Weeks Duration
| Reaction | Adverse Reaction (Preferred Term) KALYDECO N=109 n (%) | Incidence: Pooled 48-Week Trials Placebo N=104 n (%) |
|---|---|---|
| Headache | 26 (24) | 17 (16) |
| Oropharyngeal pain | 24 (22) | 19 (18) |
| Upper respiratory tract infection | 24 (22) | 14 (14) |
| Nasal congestion | 22 (20) | 16 (15) |
| Abdominal pain | 17 (16) | 13 (13) |
| Nasopharyngitis | 16 (15) | 12 (12) |
| Diarrhea | 14 (13) | 10 (10) |
| Rash | 14 (13) | 7 (7) |
| Nausea | 13 (12) | 11 (11) |
| Dizziness | 10 (9) | 1 (1) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following adverse reactions are discussed in greater detail in other sections of the labeling: Transaminase Elevations [ see Warnings and Precautions (5.1) ] Hypersensitivity Reactions, Including Anaphylaxis [see Warnings and Precautions (5.2) ] Intracranial Hypertension [see Warnings and Precautions (5.3) ] Neuropsychiatric Events, Including Suicidal Thoughts and Behaviors [see Warnings and Precautions (5.4) ] Cataracts [see Warnings and Precautions (5.6) ] The most common adverse drug reactions to KALYDECO (≥8% of patients with CF who have a G551D mutation in the CFTR gene) were headache, oropharyngeal pain, upper respiratory tract infection, nasal congestion, abdominal pain, nasopharyngitis, diarrhea, rash, nausea, and dizziness. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Vertex Pharmaceuticals Incorporated at 1-877-634-8789 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. …
Source: FDA drug label, Vertex Pharmaceuticals Incorporated, effective March 23, 2026 (SPL set 0ab0c9f8-3eee-4e0f-9f3f-c1e16aaffe25), via openFDA; the full label on DailyMed
What do FAERS reports show?
7,897 reports list ivacaftor among the medicines taken, each a report of something that happened, not proof the medicine caused it; 325 are coded as a death and 4,375 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 19 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Ivacaftor: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions