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CFTR Potentiator — Cystic Fibrosis Pregnancy: Limited data — use only if clearly indicated; CF requires specialist management in pregnancy; consult CF centre

Ivacaftor

Brand names: Kalydeco

Adult dose

Dose: 150 mg twice daily
Route: Oral (with fat-containing food — e.g. eggs, butter, peanut butter)
Frequency: Every 12 hours
Max: 150 mg twice daily
CFTR potentiator for cystic fibrosis with gating mutations (G551D — most common — and other responsive mutations listed in SPC). Does not benefit F508del homozygous patients (CFTR not trafficked to cell surface). Requires CFTR mutation testing before prescribing.

Paediatric dose

Dose: Age/weight-based: 6 months–<6 years — weight-based (50 mg granules for <14 kg; 75 mg for ≥14 kg); 6 years+ — 150 mg BD mg/kg
Route: Oral with fatty food
Frequency: Every 12 hours
Max: 150 mg twice daily (≥6 years)
BNFc: licensed from 4 months of age for eligible mutations. Granule formulation (50 mg, 75 mg) for infants/young children — sprinkle on soft food. Tablet from 6 years.

Dose adjustments

Renal

No dose adjustment required in mild-moderate renal impairment

Hepatic

Reduce to 150 mg once daily in moderate hepatic impairment; use 150 mg once daily (or less) in severe impairment — hepatic metabolism

Paediatric weight-based calculator

BNFc: licensed from 4 months of age for eligible mutations. Granule formulation (50 mg, 75 mg) for infants/young children — sprinkle on soft food. Tablet from 6 years.

Clinical pearls

  • First disease-modifying CFTR modulator — treats the underlying protein defect rather than symptoms; transformed care for ~5% of CF patients with gating mutations
  • G551D mutation: most common gating mutation (~4% of CF patients); ivacaftor dramatically improves FEV1, reduces exacerbations, reduces sweat chloride to near-normal
  • STRIVE trial: ivacaftor improved FEV1 by 10.6 percentage points and reduced sweat chloride by 48 mmol/L at 48 weeks — sustained response
  • Itraconazole/voriconazole interaction: potent CYP3A4 inhibition dramatically increases ivacaftor exposure — reduce to 150 mg TWICE WEEKLY (not twice daily); critical dosing change
  • Ophthalmology review at baseline and annually: cataracts reported in children on ivacaftor — mechanism unknown; non-progressive in most cases
  • CFTR mutation testing essential — check CF Trust mutation database; ivacaftor only effective for specific gating mutations

Contraindications

  • CF mutations unresponsive to ivacaftor (F508del homozygous without combination therapy)
  • Hypersensitivity to ivacaftor

Side effects

  • Headache
  • Upper respiratory tract infections
  • Nasal congestion
  • Elevated LFTs (monitor)
  • Cataracts (non-congenital — especially in children)
  • Rash

Interactions

  • Strong CYP3A4 inhibitors (azoles — itraconazole, ketoconazole) — reduce ivacaftor dose to 150 mg twice weekly (not twice daily)
  • CYP3A4 inducers (rifampicin, carbamazepine) — avoid; dramatically reduce ivacaftor levels
  • Grapefruit juice — increases ivacaftor levels; avoid

Monitoring

  • LFTs (every 3 months for first year, then annually)
  • FEV1 and lung function at each visit
  • Sweat chloride test (response marker)
  • Ophthalmology review (children — annually)
  • CFTR mutation confirmation

Reference: BNFc; BNF 90; BNFc; STRIVE Trial (Ramsey et al. NEJM 2011); NICE TA170; SPC Kalydeco; Cystic Fibrosis Trust. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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