Strensiq Side Effects

Generic name: asfotase alfa

Medically reviewed by Drugs.com. Last updated on Mar 28, 2025.

Note: This document provides detailed information about Strensiq.

Applies to asfotase alfa: subcutaneous solution Side Effects associated with asfotase alfa. Some dosage forms listed on this page may not apply specifically to the brand name Strensiq.

Applies to asfotase alfa: subcutaneous solution.

Precautions

It is very important that your doctor check you or your child's progress at regular visits to make sure that this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

This medicine may cause serious allergic reactions, including anaphylaxis, which can be life-threatening and requires immediate medical attention. Tell your doctor right away if you or your child have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of the hands, face, or mouth after using this medicine.

This medicine may cause redistribution of body fat or thickening, depression, or indentation of the skin at the injection site after several months of using it. Make sure to follow the instructions on the proper way of injecting the medicine and to rotate the injection sites regularly. Use 2 separate injection sites when giving 2 doses of this medicine.

This medicine may cause calcium to build-up in the eyes or kidneys, which could lead to more serious unwanted effects. Check with your doctor right away if you or you child have redness or dryness of the eye, difficult or painful urination, bloody urine, nausea, vomiting, pain in the groin or genitals, sharp back pain just below the ribs, or if you or your child see floating dark spots or material before the eyes.

Asfotase alfa may possibly cause the body to develop antibodies against it, which can lessen the effects of this medicine. If your or your child's symptoms do not improve within a few days, or if they become worse, check with your doctor.

Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.

Serious side effects of Strensiq

Along with its needed effects, asfotase alfa (the active ingredient contained in Strensiq) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking asfotase alfa:

Other side effects of Strensiq

Some side effects of asfotase alfa may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to asfotase alfa: subcutaneous solution.

General adverse events

The most common adverse reactions include injection site reactions, lipodystrophy, ectopic calcifications, and hypersensitivity reactions.^[Ref]

Hypersensitivity

• Very common (10% or more): Hypersensitivity reactions (12%)
• Uncommon (0.1% to 1%): Anaphylaxis symptoms^[Ref]

In clinical trials 1 treated-patient (n=99; 1%) experienced signs and symptoms consistent with anaphylaxis. This patient had been receiving this drug for 3.5 years before this reaction occurred. The reaction (difficulty breathing, nausea, periorbital edema, and dizziness) occurred approximately 1 minute after injection and resolved without medical treatment. This patient continued on therapy with premedication and eventually continued treatment without premedication.

Hypersensitivity reactions including nausea/vomiting, fever, headache, flushing, irritability, rigor/chills, skin erythema, rash, pruritus, and oral hypoesthesia have been reported.^[Ref]

Local

• Very common (10% or more): Injection site reactions (63%), lipodystrophy (28%)^[Ref]

Localized lipodystrophy, including lipoatrophy and lipohypertrophy, has been reported after several months. The frequency of injection site reactions and lipodystrophy were higher in patients with juvenile-onset hypophosphatasia (HPP) as compared to perinatal/infantile onset HPP patients.

Injection site reactions included erythema, discoloration/hyperpigmentation, pain/tenderness, pruritus/itching, swelling, induration, macule, bruising, nodule, injection site rash, inflammation, papules, hemorrhage, hematoma, urticaria, warmth, calcification, mass, scar, and cellulitis. The majority of injection site reactions resolved within 1 week. One patient experienced a severe injection site reaction of injection site discoloration and withdrew from the clinical trial.^[Ref]

Renal

• Frequency not reported: Nephrocalcinosis, renal stones^[Ref]

In clinical trials, there were 14 cases (14%) of ectopic calcification of the eye (including the cornea and conjunctiva) and the kidneys (nephrocalcinosis). No visual changes or changes in renal function were reported as a result of these ectopic calcifications. The frequency of ectopic calcifications was higher in patients with juvenile-onset hypophosphatasia (HPP) as compared to perinatal/infantile onset HPP patients.

Renal stones have been reported in less than 1% of patients.^[Ref]

Ocular

• Frequency not reported: Ectopic calcifications of eye^[Ref]

In clinical trials, there were 14 cases (14%) of ectopic calcification of the eye (including the cornea and conjunctiva) and the kidneys (nephrocalcinosis). No visual changes or changes in renal function were reported as a result of these ectopic calcifications. The frequency of ectopic calcifications was higher in patients with juvenile-onset hypophosphatasia (HPP) as compared to perinatal/infantile onset HPP patients.^[Ref]

Hepatic

• Frequency not reported: Chronic hepatitis

Chronic hepatitis has been reported in less than 1% of patients.

Immunologic

• Frequency not reported: Anti-drug antibodies

In clinical trials, 78% (76/98) of patients tested positive for anti-drug antibodies at some point after receiving treatment. Of these patients, 45% (34/76) had neutralizing antibodies. No correlation was observed between anti-drug antibody titer and neutralizing antibody (% inhibition) values. Formation of anti-drug antibody resulted in a reduced systemic exposure.

Metabolic

• Frequency not reported: Hypocalcemia, decreased vitamin B6

Hypocalcemia and decreased vitamin B6 have been reported in less than 1% of patients

See also:

Further information

Strensiq side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

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