Laronidase can rarely cause a very serious (sometimes fatal) allergic reaction. This reaction may occur during or up to 3 hours after the infusion. Get medical help right away if you notice any symptoms of a serious allergic reaction, including: itching/swelling (especially of the face/tongue/throat), trouble breathing, severe dizziness, fainting, or rash/hives. Your health care professional will monitor you closely for any signs of allergic reactions during your infusion and for some time after.

Before you start your infusion, tell your doctor if you have a fever or an infection (such as cold or flu) or if you have a history of heart problems (such as heart failure), breathing problems, interrupted breathing during sleep (such as sleep apnea), or swelling. Your health care professional will monitor you closely to prevent these problems from getting worse, and may delay your infusion if necessary.