Strensiq – Asfotase alfa uses, dose and side effects


40 mg/ml solution for injection (12 mg/0.3 ml, 18 mg/0.45 ml, 28 mg/0.7 ml, 40 mg/1 ml)
asfotase alfa

What Strensiq is and what it is used for

What Strensiq is

Strensiq is a medicine used to treat the hereditary disease hypophosphatasia when it appears in childhood. It contains the active substance asfotase alfa.

What is hypophosphatasia

Patients with hypophosphatasia have low levels of an enzyme called alkaline phosphatase, which is important for various body functions, including for bones and teeth to become properly hard. Patients with the disease have problems with bone growth and strength, which can lead to broken bones, bone pain, and difficulty walking, as well as breathing difficulties and risk of seizures.

What Strensiq is used for

The active substance in Strensiq can replace the missing enzyme (alkaline phosphatase) in hypophosphatasia. It is used as a long-term enzyme replacement therapy to manage the symptoms.

What benefits Strensiq has shown in clinical studies

Strensiq has shown benefits for patients’ bone mineralization and growth.

What you need to know before you use Strensiq

Do not use Strensiq

If you are severely allergic to asfotase alfa (see section “Warnings and precautions” below) or any of the other ingredients of this medicine (listed in section 6).

Warnings and precautions

Talk to your doctor before starting Strensiq.

  • Patients who have received asfotase alfa have experienced allergic reactions, including life-threatening allergic reactions similar to anaphylactic reactions, which required medical treatment. Patients who have experienced anaphylaxis-like symptoms have experienced difficulty breathing, suffocation, nausea, swelling around the eyes, and dizziness. The reactions occurred within minutes of asfotase alfa injection and may occur in patients who have received asfotase alfa for more than a year. If you experience any of these symptoms, stop taking Strensiq immediately and seek medical attention.
  • If you have an anaphylactic reaction or a reaction with similar symptoms, your doctor will discuss with you what measures to take and the possibility of restarting Strensiq under medical supervision. Always follow the instructions given to you by your doctor.
  • Development of blood proteins against Strensiq, also called drug antibodies, may occur during treatment. Talk to your doctor if you feel that the effect of Strensiq is diminishing.
  • Fat pads or a decrease in the amount of fat tissue under the surface of the skin (localized lipodystrophy) have been reported at the injection site after several months in patients using Strensiq. Carefully read section 3 on injection recommendations. It is important to alternate between the following injection sites to reduce the risk of lipodystrophy: abdominal area, thigh, or upper arm.
  • In studies, some eye-related side effects have been reported that are probably related to hypophosphatasia (eg, calcium deposits in the eye [conjunctival and corneal calcification]), both in patients who used and those who did not use Strensiq. Talk to your doctor if you experience vision problems.
  • Early fusion of the bones of the skull (craniosynostosis) in children under 5 years of age has been reported in clinical trials in infants with hypophosphatasia, with and without the use of Strensiq. Talk to the doctor if you notice any change in the shape of your child’s head.
  • If you are treated with Strensiq, you may have a reaction at the injection site (pain, lump, rash, discoloration) during the injection of the medicine or in the hours after the injection. If you experience severe reactions at the injection site, talk to your doctor immediately.
  • An increased concentration of parathyroid hormones and low calcium levels have been reported in studies. For that reason, your doctor may ask you to take calcium and vitamin D supplements as needed.
  • Weight gain may occur when you are treated with Strensiq. Your doctor can give you dietary advice as needed.

Other medicines and Strensiq

Tell your doctor or pharmacist if you are using, have recently used, or might be using other medicines.

If you need to undergo laboratory tests (give blood samples), tell the doctor that you are being treated with Strensiq. Strensiq can cause some samples to show falsely higher or lower results. Therefore, a different type of test may need to be used if you are treated with Strensiq.


Strensiq should not be used during pregnancy. An effective method of contraception during treatment should be considered for women who may become pregnant.


It is unknown whether Strensiq can pass into breast milk. Tell the doctor if you are breastfeeding or plan to breastfeed. The doctor will help you decide whether to stop breastfeeding or to stop taking Strensiq, taking into account the benefit of breastfeeding for the baby and the benefit of Strensiq for the mother.

If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before using this medicine.

Driving ability and use of machinery

This medicine is not expected to have any effect on the ability to drive or use machines.

Important information about some of the excipients in Strensiq

This medicinal product contains less than 1 mmol sodium (23 mg) per vial , meaning it is essentially ‘sodium-free’.

How to use Strensiq

Always use this medicine exactly as described in this leaflet or as directed by your doctor, pharmacist, or nurse. Consult a doctor, pharmacist, or nurse if you are unsure.

A doctor experienced in treating patients with metabolic or bone-related diseases will explain to you how to use Strensiq. After receiving instructions from the doctor or a specialist nurse, you can inject Strensiq yourself at home.


  • The dose you receive is based on your body weight.
  • The correct dose is calculated by the doctor and consists of a total of 6 mg asfotase alfa per kg of body weight each week, given either as an injection of 1 mg/kg asfotase alfa 6 times per week or as 2 mg/kg asfotase alfa 3 times per week, depending on the doctor’s recommendation. Each dose is given by injection under the skin ( subcutaneously ). (The dosage chart below provides detailed information on the volume to inject and the type of bottle to use, depending on your weight.)
  • The doctor needs to adjust the dose at regular intervals as the body weight changes.
  • The maximum volume per injection must not exceed 1 ml. If more than 1 ml is needed, you should give several injections right after each other.

At 3 injections per week

Body weight (kg)Volume to be injectedColor code of the bottle to be used
30.15 mlDark blue
40.20 mlDark blue
50.25 mlDark blue
60.30 mlDark blue
70.35 mlOrange
80.40 mlOrange
90.45 mlOrange
100.50 mlLight blue
110.55 mlLight blue
120.60 mlLight blue
130.65 mlLight blue
140.70 mlLight blue
150.75 mlPink
160.80 mlPink
170.85 mlPink
180.90 mlPink
190.95 mlPink
201 mlPink
250.50 mlGreen
300.60 mlGreen
350.70 mlGreen
400.80 mlGreen

At 6 injections per week

Body weight (kg)Volume to be injectedColor code of the bottle to be used
60.15 mlDark blue
70.18 mlDark blue
80.20 mlDark blue
90.23 mlDark blue
100.25 mlDark blue
110.28 mlDark blue
120.30 mlDark blue
130.33 mlOrange
140.35 mlOrange
150.38 mlOrange
160.40 mlOrange
170.43 mlOrange
180.45 mlOrange
190.48 mlLight blue
200.50 mlLight blue
250.63 mlLight blue
300.75 mlPink
350.88 mlPink
401 mlPink
500.50 mlGreen
600.60 mlGreen
700.70 mlGreen
800.80 mlGreen
900.90 mlGreen (x2)
1001 mlGreen (x2)

Injection recommendations

  • You may react to the injection site. Read section 4 carefully to find out what side effects may occur before using this medicine.
  • For regular injections, you should vary the injection site between different parts of the body to reduce possible pain and irritation.
  • Areas with a decent amount of fat under the skin (thighs, arms [outside of the upper arms], abdomen and buttocks) are the most suitable areas to inject in. Discuss with your doctor or nurse which are the best places for you.

Read the following instructions carefully before injecting Strensiq

  • Each vial is for single use only and should be punctured only once. Strensiq liquid should be clear, slightly opalescent or opalescent, colorless to slightly yellow, and may contain some small clear or white particles. The liquid must not be used if it is discolored or contains lumps or large particles. In that case, take a new injection vial. Unused medicines and waste must be disposed of according to current instructions.
  • If you inject this medicine yourself, your doctor, pharmacist, or nurse will show you how to prepare and inject the medicine. Do not inject this medicine yourself unless you have been trained and understand the procedure.

How Strensiq is injected

Step 1: Prepare Strensiq dose one

  1. Wash your hands thoroughly with soap and water.
  2. Remove the unopened Strensiq vial(s) from the refrigerator 15 to 30 minutes before the injection is to be given to allow the liquid to reach room temperature. Do not heat Strensiq in any other way (eg in a microwave or hot water). Once the medicine has been taken out of the refrigerator, it must be used within a maximum of 3 hours.
  3. Remove the protective cap from the vial(s) of Strensiq. Remove the plastic protective sleeve from the syringe to be used.
  4. Always use a new syringe enclosed in protective plastic.
  5. Attach a larger injection needle (eg 25 G) to the empty syringe, with the protective cap still on the needle. Press firmly and turn the needle clockwise until it is securely seated on the syringe.
  6. Remove the protective cap from the needle on the syringe. Be careful not to stick yourself to the needle.
  7. Pull out the plunger so that as much air is drawn into the syringe as corresponds to your dose.

Step 2: Withdraw the Strensiq solution from the vial

1. Grasp the syringe and vial and insert the needle through the sterile rubber membrane and into the vial.
2. Push the plunger in so that all the air is emptied into the vial.

3. Turn the vial over and spray upside down. The needle should be in the liquid. Pull out the plunger until you have the correct dose in the syringe. 
4. Check that the correct volume has been drawn up and that there are no air bubbles in the syringe before withdrawing the needle from the vial. If there are bubbles in the syringe, hold the syringe with the needle pointing up, then gently tap the side of the syringe so that the bubbles float to the surface.
5. When all the bubbles are at the top of the syringe, gently push the plunger to push the bubbles out of the syringe and back into the bottle. 

6. When the bubbles have been removed, recheck the dose in the syringe and that you have drawn up the correct amount of liquid. You may need to use several vials to draw up the full amount needed for the correct dose.

Step 3: Attach the injection needle to the syringe

  1. Withdraw the needle from the vial. Replace the protective cap with one hand by placing the cap on a flat surface, inserting the needle into the cap, lifting it and snapping it securely using only one hand.
  2. Carefully remove the large injection needle by pushing in and turning counterclockwise. Discard the needle with the protective cap on in a sharps container.
  3. Attach a narrower needle (eg 27 or 29 G) to the prefilled syringe. Leave the protective cap in place, push the needle and turn clockwise until the needle is securely on the syringe. Pull the protective cap straight off the needle.
  4. Hold the syringe with the needle pointing up and tap the syringe to remove any air bubbles.

Check that the volume in the syringe is correct.

The volume per injection must not exceed 1 ml. If it does, several injections must be given at different injection sites.

You are now ready to inject the correct dose.

Step 4: Inject Strensiq

1. Choose an injection site (thighs, abdomen, arms, [outer upper arm], buttocks). The most suitable places for injection are marked in gray in the image. Your doctor will inform you about possible injection sites.
NOTE: do not use areas where you feel lumps, hard knots, or pain. Talk to your doctor if you notice anything like this.

2. Gently pinch the skin of the chosen injection area between your thumb and forefinger.

3. Holding the syringe like a pencil or dart, insert the needle into the raised skin so that its angle to the skin surface is between 45º and 90º.
For patients who have little subcutaneous fat or who have thin skin, an angle of 45º may be preferable.
4. While maintaining your grip on the skin, push the syringe plunger to inject the medicine slowly and steadily in.
5. Withdraw the needle, release the skin fold and gently press with a cotton ball or gauze over the injection site for a few seconds. This helps to close the punctured tissue and prevent leakage. Do not rub the injection site after injection.

If you need another injection to get the prescribed dose, take a new vial of Strensiq and repeat steps 1 through 4.

Step 5: Discard the remaining material

Collect the syringes, vials, and needles in a sharps container. Your doctor, pharmacist, or nurse will tell you how to access a sharps container.

If you have used too much Strensiq 

If you suspect that you have accidentally received a higher dose of Strensiq than prescribed, contact your doctor for advice.

If you forget to take Strensiq

Do not inject a double dose to make up for a missed dose. Contact your doctor for advice.

Further information is available here:

Image 9

If you have any further questions about this medicine, ask your doctor, pharmacist, or nurse.

Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them.

If you are not sure what the side effects below mean, ask the doctor to explain them to you.

The most serious side effects that have occurred in patients receiving asfotase alfa have been allergic reactions, including life-threatening allergic reactions similar to anaphylactic reactions that required medical treatment. This side effect is common (may affect up to 1 in 10 people). Patients who have experienced these severe allergic reactions have experienced difficulty breathing, choking, nausea, swelling around the eyes, and dizziness. The reactions occurred within minutes of asfotase alfa injection and may occur in patients who have used asfotase alfa for more than a year. If you experience any of these symptoms, stop using Strensiq immediately and seek medical attention.

Other allergic reactions (hypersensitivity) can also be common and appear in the form of redness ( erythema ), fever ( pyrexia ), skin rash, itching ( pruritus ), irritability, nausea, vomiting, pain, chills, numbness in the mouth ( oral hypoesthesia ), headache, facial flushing, fast pulse ( tachycardia ) and cough. If you experience any of these symptoms, stop using Strensiq immediately and seek medical attention.

Very common: may affect more than 1 in 10 people

Reactions at the injection site during injection of the drug or during the hours after injection (which may lead to redness, discoloration, itching, pain, fat pads or a reduced amount of fat tissue under the skin surface, lighter skin area [hypopigmentation of the skin] and/or swelling)

Fever ( pyrexia )


Skin redness ( erythema )

Pain in the hands and feet (pain in the extremities )

bruise (contusion)


Common: may affect up to 1 in 10 people

Tight skin, skin discoloration


Numbness in the mouth ( oral hypoesthesia )

Muscle pain ( myalgia )


Increased tendency to bruise


Injection site skin infection (injection site cellulitis )

Decreased amount of calcium in the blood ( hypocalcemia )

Kidney stones ( nephrolithiasis )

How Strensiq should be stored

Keep this medicine out of the sight and reach of children.

Use before the expiry date which is stated on the carton and vial label after EXP. The expiration date is the last day of the specified month.

Store in a refrigerator (2 °C–8 °C).

Do not freeze.

Store in the original packaging. Light sensitive.

After opening the vial, the medicine should be used immediately (within no more than 3 hours at room temperature, between 23 °C and 27 °C).

Medicines must not be thrown into the drain or among the household waste. Ask the pharmacist how to dispose of medicines that are no longer used. These measures will help to protect the environment.

Contents of the packaging and other information

Contents declaration

The active substance is asfotase alfa. Each ml of solution contains 40 mg of asfotase alfa.

Each vial of 0.3 ml solution (40 mg/ml) contains 12 mg asfotase alfa.

Each vial of 0.45 ml solution (40 mg/ml) contains 18 mg asfotase alfa.

Each vial of 0.7 ml solution (40 mg/ml) contains 28 mg asfotase alfa.

Each vial of 1 ml solution (40 mg/ml) contains 40 mg asfotase alfa.

Other ingredients are sodium chloride, monobasic sodium phosphate monohydrate, dibasic sodium phosphate heptahydrate, and water for injections.

Appearance and package sizes of the medicine

Strensiq solution for injection is a clear, slightly opalescent or opalescent, colorless to slightly yellow water-like solution in vials containing 0.3 ml, 0.45 ml, 0.7 ml, and 1 ml of solution. Some small transparent or white particles may be present.

Pack sizes of 1 or 12 vials.

Not all pack sizes may be marketed.

Marketing Authorisation Holder

Alexion Europe SAS

103-105 rue Anatole France

92300 Levallois-Perret



Alexion Pharma International Operations Unlimited Company

College Business and Technology Park, Blanchardstown

Dublin 15


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