CFTR Potentiator — Cystic Fibrosis Pregnancy: There are no or limited data (less than 300 pregnancy outcomes) from use in pregnant women; animal studies do not indicate reproductive toxicity. As a precautionary measure it is preferable to avoid use during pregnancy. Breast-feeding: it is unknown whether ivacaftor is excreted in human milk (it is excreted in rat milk) so a risk to the infant cannot be excluded - decide whether to discontinue breast-feeding or ivacaftor.

Ivacaftor

Brand names: Kalydeco

A CFTR potentiator used in cystic fibrosis for patients with specific gating (and certain other) mutations in the CFTR gene. It is a precision therapy whose suitability depends on the individual's genotype.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 150 mg every 12 hours (300 mg total daily dose) for adults and patients aged 6 years and older

Route: Oral - one 150 mg tablet taken with fat-containing food

Frequency: Every 12 hours (twice daily)

SOURCE NOTE: the adult figure above is from the US Kalydeco prescribing information (openFDA), because the UK SPC fetched is 'Kalydeco 13.4 mg granules in sachet', whose dosing table covers only patients below 25 kg and states 'greater than or equal to 25 kg: See Kalydeco tablets SmPC for further details'. The UK Kalydeco tablets SmPC was not fetched - clinician to confirm the UK adult regimen against it. Indication is cystic fibrosis: ivacaftor should only be prescribed by physicians with experience in the treatment of cystic fibrosis, and if the genotype is unknown an accurate and validated genotyping method should be performed before starting to confirm an indicated CFTR mutation in at least one allele; the phase of the poly-T variant identified with the R117H mutation should be determined per local clinical recommendation. Take with fat-containing food; avoid food or drink containing grapefruit. Missed dose (UK SPC): if 6 hours or less have passed, take as soon as possible then take the next dose at the regularly scheduled time; if more than 6 hours have passed, wait until the next scheduled dose. Hepatic impairment (US labelling, patients 6 years and older): no adjustment in mild (Child-Pugh A); moderate (Child-Pugh B) 150 mg orally once daily; severe (Child-Pugh C) not studied, use with caution - the UK SPC states use in severe hepatic impairment is not recommended unless benefits outweigh risks, with reduced dosing and intervals modified to clinical response. CYP3A: dosing must be reduced with moderate or strong CYP3A inhibitors. Monotherapy is not recommended in patients homozygous for the F508del mutation - a phase 2 study showed no statistically significant difference in FEV1 over 16 weeks versus placebo. Clinical efficacy in patients with the G970R mutation could not be established; less evidence of a positive effect was shown for the R117H-7T mutation. Liver monitoring: assess ALT, AST and total bilirubin before starting, every 3 months during the first year and annually thereafter; interrupt dosing for ALT or AST greater than 5 x ULN, or greater than 3 x ULN with bilirubin greater than 2 x ULN. Paediatric dosing is by age and weight band using granule sachets (see the ivacaftor_paed draft) - no per-kg dose is stated.

Dose adjustments

Renal

No dose adjustment is necessary for mild to moderate renal impairment. Caution is recommended in severe renal impairment (creatinine clearance less than or equal to 30 mL/min) or end-stage renal disease.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients (UK SPC section 4.3; the US labelling states 'None')

Side effects

Headache (23.9%) and dizziness - very common
Oropharyngeal pain (22.0%), upper respiratory tract infection (22.0%), nasal congestion (20.2%) - very common; nasopharyngitis (14.7%)
Abdominal pain (15.6%) and diarrhoea (12.8%) - very common
Transaminase elevations (12.8% vs 11.5% on placebo) - very common; liver injury and total bilirubin elevations reported (frequency not known), including liver failure leading to transplantation in patients on the ivacaftor/tezacaftor/elexacaftor combination regimen
Rash (12.8%) and bacteria in sputum (12.8%) - very common

Interactions

Moderate or strong CYP3A inhibitors (e.g. fluconazole; ketoconazole, itraconazole, posaconazole, voriconazole, telithromycin, clarithromycin) - ivacaftor is a sensitive CYP3A substrate; ketoconazole increased ivacaftor AUC 8.5-fold and fluconazole 3-fold, so the dose must be reduced in patients aged 6 months and older
Ivacaftor is not recommended in patients aged 1 month to less than 6 months taking concomitant strong or moderate CYP3A inhibitors
Food or drink containing grapefruit should be avoided during treatment

Clinical monograph

How it works

Ivacaftor potentiates the defective CFTR channel at the cell surface, increasing the probability that the gate stays open and enhancing chloride transport to improve mucus hydration and clearance.

Prescribing in practice

Confirm an appropriate responsive CFTR mutation before prescribing, as it is ineffective in patients without a suitable genotype.
It is metabolised by CYP3A and interacts with strong inducers and inhibitors, so dose adjustment or avoidance may be needed with such co-medication and grapefruit should be avoided.
Transaminase elevations can occur, so monitor liver function, and baseline and periodic ophthalmological review is advised in children for lens changes.

Monitoring

Monitor liver enzymes before and during treatment, alongside respiratory function and clinical response, with eye review in paediatric patients.

Counselling the patient

Take it with fat-containing food to aid absorption and avoid grapefruit and Seville oranges.
Report yellowing of the skin or eyes, abdominal pain or unusual tiredness.

Evidence & guidelines

Ivacaftor is approved for gating-mutation cystic fibrosis and is commissioned in the UK through specialist CF services per NICE arrangements.

Reference: STRIVE Trial (Ramsey et al. NEJM 2011); NICE TA170; SPC Kalydeco; Cystic Fibrosis Trust; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways