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Haemoglobin S Polymerisation Inhibitor — Sickle Cell Disease Pregnancy: Limited data — avoid unless clearly indicated; discuss with haematology and obstetric team

Voxelotor

Brand names: Oxbryta

Adult dose

Dose: 1500 mg once daily
Route: Oral
Frequency: Once daily with or without food
Max: 1500 mg/day
Indicated for haemolytic anaemia in sickle cell disease in adults and children ≥4 years. Stabilises oxyhaemoglobin conformation, preventing HbS polymerisation and red cell sickling. Raises Hb and reduces haemolysis markers — does not directly reduce VOC rate (as primary endpoint).

Paediatric dose

Dose: Weight-based: 40–<50 kg — 1000 mg once daily; ≥50 kg — 1500 mg once daily; 20–<40 kg — 900 mg once daily; 10–<20 kg — 600 mg once daily mg/kg
Route: Oral
Frequency: Once daily
Max: 1500 mg/day
BNFc: licensed from 4 years of age. Tablet and dispersible tablet formulations. Weight-based dosing per prescribing information.

Dose adjustments

Renal

No dose adjustment required

Hepatic

Reduce to 1000 mg once daily in severe hepatic impairment

Paediatric weight-based calculator

BNFc: licensed from 4 years of age. Tablet and dispersible tablet formulations. Weight-based dosing per prescribing information.

Clinical pearls

  • HOPE trial: voxelotor 1500 mg significantly increased Hb by ≥1 g/dL in 51% of patients vs 7% placebo; reduced indirect bilirubin and reticulocyte count (markers of haemolysis)
  • Raises Hb by shifting haemoglobin to the oxygenated conformation — increases oxygen affinity (may theoretically impair oxygen delivery; clinical significance uncertain)
  • Does not directly reduce VOC rate as primary endpoint — complements crizanlizumab (different mechanisms) and hydroxycarbamide
  • NICE TA743 (2022): approved for sickle cell disease with haemolytic anaemia in adults and children ≥12 years when hydroxycarbamide is not appropriate
  • Tablet can be dispersed in water for patients unable to swallow — ask pharmacist for dispersible formulation
  • Monitoring Hb improvement expected within 4–8 weeks of starting

Contraindications

  • Hypersensitivity to voxelotor
  • Pregnancy (limited data)

Side effects

  • Headache
  • Diarrhoea
  • Abdominal pain
  • Nausea
  • Fatigue
  • Rash

Interactions

  • Strong CYP3A4 inhibitors — increase voxelotor exposure; reduce dose to 1000 mg/day
  • Strong CYP3A4 inducers — reduce voxelotor efficacy; avoid
  • Sensitive CYP3A4 substrates — voxelotor is a weak CYP3A4 inhibitor; monitor

Monitoring

  • Hb (baseline and every 4–8 weeks until stable, then every 3 months)
  • Haemolysis markers (LDH, indirect bilirubin, reticulocytes)
  • LFTs

Reference: BNFc; BNF 90; BNFc; HOPE Trial (Vichinsky et al. NEJM 2019); NICE TA743; SPC Oxbryta. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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