Recombinant α-L-iduronidase Pregnancy: US label: available data from the MPS I Registry pregnancy sub-registry, published case reports and the global pharmacovigilance database in more than 30 pregnant women have not identified a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes; continuation of treatment during pregnancy should be individualised. An MPS I pregnancy sub-registry exists.

Laronidase

Brand names: Aldurazyme

Laronidase is a recombinant enzyme replacement therapy used for the long-term treatment of mucopolysaccharidosis type I (Hurler, Hurler-Scheie and Scheie syndromes).

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: 0.58 mg/kg (actual body weight) once weekly

Route: Intravenous infusion. Must be diluted with 0.9% sodium chloride injection to a final volume of 50 mL, 100 mL or 250 mL determined by body weight and cardiopulmonary condition (body weight 2 kg to under 4 kg: 50 mL; 4 kg up to 20 kg: 100 mL; greater than 20 kg: 250 mL).

Frequency: Once weekly

No UK SPC was retrieved in this bundle; dose taken from US prescribing information for ALDURAZYME (Genzyme) - verify against the UK SPC before publication. INFUSION RATE (exact units as stated): initial infusion rate 10 micrograms/kg/hour, which may be increased every 15 minutes during the first hour as tolerated to a maximum infusion rate of 200 micrograms/kg/hour; the maximum rate is then maintained for the remainder of the infusion (2 to 3 hours). For patients with underlying cardiac or respiratory compromise weighing up to 30 kg, physicians may consider diluting in a volume of 100 mL and administering at a decreased infusion rate. Premedication: consider premedicating with antihistamines, with or without antipyretics, 60 minutes before the start of infusion. Appropriate medical monitoring and support measures, including cardiopulmonary resuscitation equipment, should be readily available during administration. Missed doses: restart treatment as soon as possible and maintain the 1-week interval between infusions thereafter; do not double a dose to compensate for a missed dose. Reaction management: for a severe hypersensitivity reaction (e.g. anaphylaxis) or severe infusion-associated reaction, immediately discontinue and treat; for mild to moderate reactions, consider holding the infusion for 15 to 30 minutes or slowing the rate by 25% to 50%, then resuming at a 25% to 50% reduced rate as tolerated and increasing by increments of 25% with subsequent infusions.

Paediatric dose

Dose: 0.58 mg/kg

Route: Intravenous infusion

Frequency: Once weekly

Max: No absolute dose cap stated; maximum infusion rate 200 micrograms/kg/hour

The US label states a single actual-body-weight dose for all patients rather than a separate paediatric regimen; §8.4 states safety and effectiveness have been established for paediatric patients with the Hurler and Hurler-Scheie forms of MPS I and for paediatric patients with the Scheie form who have moderate to severe symptoms, and that safety and effectiveness in patients 6 months to 5 years of age was similar to those 6 to 18 years of age and adults. Safety and effectiveness in mildly affected paediatric patients with the Scheie form have not been established. Infusion volume by weight: 2 kg to under 4 kg = 50 mL; 4 kg up to 20 kg = 100 mL; over 20 kg = 250 mL. US labelling only - clinician to verify against the UK SPC and a children's formulary before use.

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 (US label section 4 states 'None')

Side effects

Infusion-associated reactions - pyrexia, chills, blood pressure increased, tachycardia, oxygen saturation decreased (most common, 10% or more, in patients 6 months and older)
Hypersensitivity reactions including anaphylaxis, reported during or up to 3 hours after infusion (respiratory failure, respiratory distress, stridor, tachypnoea, bronchospasm, obstructive airways disorder, hypoxia, hypotension, bradycardia, urticaria)
Rash; injection site reaction (10% or more in patients 6 years and older)
Upper respiratory tract infection
Hyperreflexia, paraesthesia, flushing and poor venous access (10% or more in patients 6 years and older)

Clinical monograph

How it works

It is a recombinant form of human alpha-L-iduronidase that replaces the deficient enzyme, enabling lysosomal breakdown of accumulated glycosaminoglycans (dermatan and heparan sulphate).

Prescribing in practice

Infusion-associated and hypersensitivity reactions can occur, so it is given as a controlled intravenous infusion with appropriate premedication and facilities to manage reactions.
Slow the infusion rate or interrupt treatment if reactions develop, and observe the patient during and after administration.
It does not cross the blood-brain barrier and so does not treat the central nervous system manifestations of the disease.

Monitoring

Monitor for infusion reactions and assess clinical response, including respiratory and functional outcomes, over the course of treatment.

Counselling the patient

Treatment is given as a regular infusion in a supervised setting and continues long term.
Report any reaction during infusion such as flushing, rash, breathlessness or fever.
This therapy controls many systemic features but does not address effects on the brain.

Evidence & guidelines

Enzyme replacement with laronidase is the established disease-specific treatment for mucopolysaccharidosis type I.

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