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Tumour Lysis Syndrome Pregnancy: Contraindicated — animal toxicity; avoid in pregnancy and breastfeeding

Rasburicase

Brand names: Fasturtec

Adult dose

Dose: 0.2 mg/kg once daily for up to 7 days
Route: Intravenous infusion over 30 minutes
Frequency: Once daily
Max: 0.2 mg/kg/day for maximum 7 days
Recombinant urate oxidase. Converts uric acid to allantoin (5x more soluble) — dramatically lowers serum urate within hours. Used for prevention and treatment of tumour lysis syndrome (TLS) in haematological malignancies. Blood samples must be collected on ice and processed immediately — rasburicase continues to degrade uric acid ex vivo at room temperature.

Paediatric dose

Dose: 0.2 mg/kg
Route: IV infusion over 30 minutes
Frequency: Once daily for up to 7 days
Max: 0.2 mg/kg/day
Same dosing as adults. Licensed for children and adolescents. G6PD screening mandatory before use — haemolytic anaemia risk.

Dose adjustments

Renal

No dose adjustment required — not renally cleared; used specifically to prevent AKI from TLS

Hepatic

No dose adjustment required

Paediatric weight-based calculator

Same dosing as adults. Licensed for children and adolescents. G6PD screening mandatory before use — haemolytic anaemia risk.

Clinical pearls

  • G6PD screening is MANDATORY before first dose — rasburicase produces hydrogen peroxide as a by-product of uric acid oxidation, which causes oxidative haemolysis in G6PD-deficient red cells. Can be fatal.
  • Blood sample handling: the ONE clinical factoid examiners love — rasburicase degrades uric acid ex vivo at room temperature. Specimens must be collected in pre-chilled tubes, transported on ice, and processed within 4 hours. Failing to do so results in falsely low (or undetectable) uric acid values.
  • Cairo-Bishop TLS criteria: laboratory TLS = 2+ of the following (25% rise from baseline or above normal threshold): uric acid >476 micromol/L, K >6 mmol/L, phosphate >1.45 mmol/L, calcium <1.75 mmol/L, or creatinine >1.5x ULN. Rasburicase rapidly corrects hyperuricaemia.
  • Single-dose rasburicase: in lower-risk patients, a single dose of 3-7.5 mg (fixed dose) followed by allopurinol has been used off-label to reduce cost while maintaining efficacy
  • Allopurinol vs rasburicase for TLS: allopurinol prevents new urate formation but does not clear existing urate load (hours to days latency). Rasburicase clears urate within 4 hours — preferred for high-risk TLS or established hyperuricaemia.

Contraindications

  • G6PD deficiency (ABSOLUTE — methaemoglobinaemia and haemolytic anaemia; screen before use)
  • Pregnancy (animal studies show toxicity)
  • Hypersensitivity to rasburicase or uricases
  • Previous serious hypersensitivity to rasburicase

Side effects

  • Hypersensitivity/anaphylaxis (up to 4.3%)
  • Haemolytic anaemia (G6PD-deficient patients)
  • Methaemoglobinaemia (G6PD deficiency)
  • Fever
  • Nausea/vomiting
  • Rash

Interactions

  • None clinically significant — but note blood sampling artefact: rasburicase degrades uric acid in blood samples at room temperature; samples must be on ice and processed immediately for accurate uric acid measurement

Monitoring

  • Serum uric acid (on ice — blood sample protocol essential)
  • Creatinine and eGFR
  • Potassium, phosphate, calcium (TLS electrolytes)
  • LDH
  • G6PD status (before first dose)

Reference: BNFc; BNF 90; BNFc; Cairo-Bishop TLS Criteria; NICE Haematology Guidelines; SPC Fasturtec. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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