Idursulfase belongs to the class of medications called enzyme replacement therapies (ERT). It is used to help improve walking capacity for people with Hunter syndrome, or mucopolysaccharidosis II (MPS II).

Hunter syndrome is a genetic condition where the body does not produce enough of the enzyme iduronate-2-sulfatase. This causes the buildup of substances called glycosaminoglycans (GAG) in cells and tissues. Idursulfase works by increasing the amounts of enzyme, which then helps to remove GAG and reduce the accumulation of GAG in the body.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop receiving this medication without consulting your doctor.

The usual dose of idursulfase is based on body weight at 0.5 mg per kg. It is given every week by intravenous (into a vein) infusion, usually over 1 to 3 hours. Idursulfase is always prepared and given by a health care professional.

It is important to receive this medication exactly as prescribed by your doctor. If you cannot keep an appointment to receive your medication, contact your doctor for advice.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are receiving the medication without consulting your doctor.

This medication is stored in the refrigerator at 2°C to 8°C and should be kept out of the reach of children. Do not freeze or shake this medication.

Each single use vial of sterile, aqueous, clear to slightly opalescent, colourless solution contains a 2 mg per mL of solution of idursulfase protein (6 mg in an extractable volume of 3 mL). The concentrate must be further diluted. Nonmedicinal ingredients: polysorbate 20, sodium chloride, sodium phosphate dibasic (heptahydrate), sodium phosphate monobasic (monohydrate), and water for injection.

Idursulfase should not be used by anyone who is allergic to idursulfase or to any of the ingredients of the medication or the container.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• eczema
• flushing
• headache
• heartburn
• dizziness and lightheadedness when rising from a sitting or lying position
• increased tear production
• joint pain
• nausea
• tremor
• upper abdominal pain

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• difficulty breathing
• dizziness
• facial swelling
• fever
• infusion reactions (e.g., headache, rash, itching, flushing, redness, hives, high blood pressure)
• increased blood pressure
• itchiness
• skin rash or hives
• swelling at the place of injection
• swelling of the feet, ankles, or hands

Stop taking the medication and seek immediate medical attention if any of the following occur:

• abnormal heart rhythm (skipped or extra heartbeats)
• bluish skin colour (e.g., lips)
• chest pain
• seizures
• signs of a blood clot in the lung (e.g., difficulty breathing, cough, chest pain, increased breathing rate)
• signs of a severe allergic reaction (e.g., hives; difficulty breathing; wheezing; dizziness; seizure; swelling of the face, lips, tongue, or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic reactions: This medication can cause serious allergic reactions that can be life-threatening. If you experience hives; difficulty breathing; bluish skin; seizures; severe dizziness; or swelling of the face, tongue, mouth, or lips while receiving this medication, get immediate medical attention. In some cases, people who have had an allergic reaction to this medication will get more allergy symptoms after the infusion has stopped. If this occurs, get immediate medical attention.

Infusion-related reactions: Infusion-related reactions caused by this medication can include skin rash, itchy skin, fever, headache, flushing, hives, and high blood pressure. If these occur, your doctor may suggest that the infusion be slowed down or stopped temporarily. Your doctor may also recommend medications such as antihistamines and corticosteroids to reduce or prevent infusion-related reactions.

Lung problems: People with poor lung function or other lung problems may be more likely to experience infusion-related reactions. Infusion-related reactions include headache, rash, itchy skin, red skin, and high blood pressure. Your doctor will monitor you closely if you have lung problems and are receiving this medication.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if idursulfase passes into breast milk. If you are breast-feeding and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children less than 16 months of age.

Seniors: The safety and effectiveness of using this medication have not been established for seniors.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. In many cases, interactions are intended or are managed by close monitoring. Speak to your doctor about how any drug interactions are being managed or should be managed.