Recombinant iduronate-2-sulfatase Pregnancy: There are no adequate and well-controlled studies in pregnant women, and available postmarketing data are insufficient to inform drug-associated risks for major birth defects, miscarriage or adverse maternal or fetal outcomes. In an animal reproduction study, no evidence of adverse effects on pre- and post-natal development was observed in rats at about 4 times the recommended human weekly dose of 0.5 mg/kg based on body surface area.

Idursulfase

Brand names: Elaprase

Idursulfase is a recombinant enzyme replacement therapy for mucopolysaccharidosis type II (Hunter syndrome).

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: 0.5 mg/kg of body weight

Route: Intravenous infusion — the calculated volume added to a 100 mL bag of 0.9% sodium chloride injection and given through a low-protein-binding infusion set with a low-protein-binding 0.2 micrometre in-line filter

Frequency: Once weekly

NO UK SPC IN BUNDLE — dose taken from US labelling (ELAPRASE, Takeda); verify against the UK SPC. The total volume of infusion should be administered over a period of 3 hours, which may be gradually reduced to 1 hour if no hypersensitivity reactions are observed; patients may require longer infusion times if hypersensitivity reactions occur, but infusion times should not exceed 8 hours. The initial infusion rate should be 8 mL per hour for the first 15 minutes; if well tolerated, the rate may be increased by 8 mL per hour increments every 15 minutes, and the infusion rate should not exceed 100 mL per hour. The infusion rate may be slowed, temporarily stopped or discontinued for that visit in the event of hypersensitivity reactions. Must not be infused with other products in the infusion tubing. Serious hypersensitivity reactions including anaphylaxis have occurred during and up to 24 hours after infusion — ensure personnel administering the product are adequately trained in cardiopulmonary resuscitative measures and have ready access to emergency medical services. Patients with compromised respiratory function or acute febrile or respiratory illness may be at higher risk of life-threatening complications; consider delaying the infusion.

Paediatric dose

Dose: 0.5 mg/kg

Route: Intravenous infusion

Frequency: Once weekly

The US label states a single weight-based dosage (0.5 mg/kg once weekly) and gives no separate paediatric regimen. Clinical trials were conducted in 96 patients with Hunter syndrome aged 5 to 31 years with the majority in the paediatric age group (median age 15 years), plus an open-label uncontrolled trial in 28 patients aged 16 months to 7.5 years. Safety and effectiveness have NOT been established in paediatric patients less than 16 months of age, and there are no data to support improvement in disease-related symptoms or long-term outcome in patients 16 months to 5 years. Patients aged 7 years and younger with complete gene deletion, large gene rearrangement, nonsense, frameshift or splice-site mutations experienced a higher incidence of hypersensitivity reactions, serious adverse reactions and anti-idursulfase antibody development. Verify against a children's formulary.

Dose auto-extracted from 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.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

None stated (US label §4 states: None)

Side effects

Hypersensitivity reactions — the most common reactions requiring medical intervention, including rash, urticaria, pruritus, flushing, pyrexia and headache
Headache (>= 9% in patients aged five years and older)
Pruritus and urticaria (>= 9% in patients aged five years and older)
Musculoskeletal pain (>= 9% in patients aged five years and older)
Diarrhoea and cough (>= 9% in patients aged five years and older)
Pyrexia, rash, vomiting and urticaria (>= 10% in patients aged seven years and younger)

Clinical monograph

How it works

It provides the deficient enzyme iduronate-2-sulfatase, enabling catabolism of dermatan and heparan sulfate and reducing glycosaminoglycan accumulation.

Prescribing in practice

Serious infusion-related and anaphylactoid reactions can occur, so give under supervision with resuscitation facilities and monitor closely during and after infusion.
It should be initiated and supervised by a clinician experienced in lysosomal storage disorders.
It does not cross the blood-brain barrier and so does not treat central nervous system manifestations of the disease.

Monitoring

Monitor for hypersensitivity reactions with each infusion and review clinical response, including respiratory and functional measures, over time.

Counselling the patient

Infusions are given regularly with monitoring for reactions such as rash, fever or breathing difficulty.
Tell staff at once if you or your child feel unwell during an infusion.
This treatment helps systemic symptoms but does not reverse intellectual or neurological effects.

Evidence & guidelines

Enzyme replacement for Hunter syndrome is an established orphan therapy supported by randomised controlled trial data.

Reference: SmPC; 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.

Pathways