Asfotase Alfa
Asfotase alfa is an enzyme replacement therapy used to treat hypophosphatasia (HPP), a rare inherited condition that impairs bone and tooth development, in patients with perinatal/infantile- and juvenile-onset disease.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Strensiq carries a boxed warning — the FDA's most serious safety alert — for life-threatening allergic reactions, including anaphylaxis. These severe reactions have happened both early in treatment and after more than a year of use. Signs to watch for include sudden difficulty breathing, a choking feeling, nausea, swelling around the eyes, or dizziness. If any of these occur, stop the injection, call 911, and seek emergency care immediately. Because of this risk, your first doses should be given under the supervision of a healthcare provider who can respond to an emergency. Always keep emergency contact information handy and make sure people around you know the warning signs.
📖 Asfotase Alfa: Patient Information Guide
A plain-language walkthrough of Asfotase Alfa — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Asfotase alfa is an enzyme replacement therapy with one approved set of uses across its supported product, Strensiq.
- Strensiq (subcutaneous injection) is approved to treat perinatal/infantile-onset hypophosphatasia (HPP) — a form of this rare genetic bone disease that appears at or around birth
- Strensiq (subcutaneous injection) is approved to treat juvenile-onset hypophosphatasia (HPP) — a form of the disease that appears during childhood
⚙️How it works▾
HPP is caused by a deficiency in an enzyme called TNSALP (tissue nonspecific alkaline phosphatase). Without enough TNSALP, a molecule called inorganic pyrophosphate (PPi) builds up outside of cells and blocks the growth of hydroxyapatite crystals — the building blocks of bone. This leads to poor bone mineralization, causing rickets and bone deformities in infants and children, and soft bones (osteomalacia) in older patients, along with muscle weakness. Asfotase alfa replaces the deficient TNSALP enzyme, reducing PPi levels and allowing bones to mineralize more normally.
💊How it's taken▾
Strensiq is given as a subcutaneous (under-the-skin) injection, typically several times per week. The injection schedule — either three or six times per week — is determined by your prescriber based on your specific situation and how well the medication is tolerated. Injection site reactions can sometimes limit how often injections are given. Injection sites should be rotated regularly to reduce the risk of skin and fat tissue changes. Always follow your prescriber's dosing instructions exactly; do not adjust your schedule without guidance.
- Take the vial out of the refrigerator 15–30 minutes before injecting to let it warm to room temperature naturally
- Strensiq vials are single-use; discard any leftover medication after each dose
- Administer within 3 hours of removing the vial from the refrigerator
🤒Side effects — in detail▾
The most common side effects of Strensiq involve the injection site and occur in the majority of patients.
- Injection site reactions — redness, pain, swelling, itching, discoloration, or skin hardening; most resolve within a week
- Lipodystrophy — changes in fat tissue at injection sites, including dimpling (lipoatrophy) or lump formation (lipohypertrophy); more common in juvenile-onset patients
- Ectopic calcifications — calcium deposits forming in the eyes (conjunctiva or cornea) or kidneys; also more common in juvenile-onset patients
- Hypersensitivity reactions — vomiting, fever, flushing, rash, chills, headache, or itching
- Nausea
- Bruising at the injection site
Serious reactions include anaphylaxis (severe allergic reaction with breathing difficulty and dizziness) — seek emergency help immediately if these occur. In some patients, antibodies that form against the medication may reduce its effectiveness over time.
⚠️Warnings & precautions▾
- Anaphylaxis and severe allergic reactions: Life-threatening allergic reactions have occurred — sometimes within minutes of an injection and sometimes after more than a year of treatment. Strensiq must be started under medical supervision. Signs include trouble breathing, choking sensation, eye swelling, nausea, and dizziness. Stop the injection and call emergency services immediately if these occur.
- Lipodystrophy: Fat tissue changes at injection sites have been reported after several months of treatment. Rotating injection sites and using proper technique reduces this risk.
- Ectopic calcifications: Calcium deposits can form in the eyes and kidneys in patients with HPP, including those treated with Strensiq. Regular eye exams and kidney ultrasounds are recommended during treatment.
- Immune-mediated effects: Most patients develop antibodies against asfotase alfa during treatment. In some cases, these antibodies may reduce how well the medication works, leading to a return or worsening of HPP symptoms after initial improvement. Contact your prescriber if you notice disease progression.
- Laboratory test interference: Strensiq can interfere with tests that use ALP as a detection reagent. Always inform lab personnel you are on this medication.
🔀What it interacts with▾
Asfotase alfa does not have traditional drug-drug interactions, but it can significantly interfere with certain laboratory tests.
- Lab tests using alkaline phosphatase (ALP) as a detection reagent: Strensiq can cause false or erroneous results in tests that use ALP-conjugated systems — including tests for hormones, bacterial antigens, and antibodies. Always tell your lab that you are taking Strensiq so they can use an alternative testing method.
- Serum ALP blood levels: ALP readings in your blood will naturally be elevated while on Strensiq because the drug itself is an ALP enzyme. These elevated readings should not be used to make clinical decisions — your prescriber is aware of this.
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- History of allergic reactions to enzyme replacement therapies: Tell your doctor before starting Strensiq — severe and life-threatening reactions have occurred
- Pregnancy: There are no adequate human data on the safety of Strensiq during pregnancy; discuss the risks and benefits with your prescriber
- Breastfeeding: It is unknown whether asfotase alfa passes into breast milk; weigh the benefits of breastfeeding against potential risks with your doctor
- Children under 40 kg: The 80 mg/0.8 mL vial of Strensiq must NOT be used in pediatric patients weighing less than 40 kg, as it delivers lower drug levels that may be inadequate for smaller patients
- Adults aged 65 and over: No clinical trial data are available for patients 65 and older with perinatal/infantile- or juvenile-onset HPP; it is unknown if they respond differently
- Ongoing monitoring: Baseline and periodic eye exams and kidney ultrasounds are recommended for all patients on Strensiq
📡Pharmacodynamics — effects in the body▾
In patients treated with Strensiq, blood levels of key TNSALP substrates — including inorganic pyrophosphate (PPi) and pyridoxal 5'-phosphate (PLP) — decrease within 6 to 12 weeks of starting treatment. Bone biopsy data from both perinatal/infantile- and juvenile-onset HPP patients showed reductions in unmineralized bone tissue, indicating improved bone mineralization during treatment. Note that reductions in PPi and PLP blood levels did not directly predict individual clinical outcomes.
🔬Pharmacokinetics — how your body processes it▾
After subcutaneous injection, asfotase alfa reaches steady-state blood levels as early as three weeks after the first dose. The elimination half-life — how long it takes the body to clear half the drug — is approximately 5 days. Dosing is based on body weight because weight is the main factor affecting how quickly the drug is cleared. An important formulation note: the higher-concentration 80 mg/0.8 mL vial delivers about 25% lower drug exposure compared to the lower-concentration vials at the same dose, which is why it should not be used in smaller pediatric patients. Development of antibodies against the medication can also reduce how much drug remains active in the body.
📦How to store it▾
stored in the original carton until the time of use under refrigerated conditions at 2°C to 8°C (36°F to 46°F) and protected from light. refrigeration, STRENSIQ should be administered within 3 hours. DO NOT FREEZE OR SHAKE.
📄 Written from Asfotase Alfa’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Asfotase Alfa — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is hypophosphatasia and why does my child need this medication? ▾
How often does Strensiq need to be injected, and where on the body? ▾
What side effects should I watch for at the injection site? ▾
Is there any risk of a serious allergic reaction? What should I watch for? ▾
Do I need any special monitoring while my child is on Strensiq? ▾
What happens if my child's symptoms start coming back after the medication seemed to be working? ▾
Is Asfotase Alfa available over the counter? ▾
When was Asfotase Alfa first available? ▾
Who makes Asfotase Alfa? ▾
💬 Answers drafted from Asfotase Alfa’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Asfotase Alfa comes
Asfotase Alfa is available in 2 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Injection
How this form is used
- Strensiq is approved to treat perinatal/infantile-onset hypophosphatasia (HPP) via subcutaneous injection
- Strensiq is approved to treat juvenile-onset hypophosphatasia (HPP) via subcutaneous injection
- Strensiq is injected under the skin (subcutaneously) — typically three or six times per week as directed by your prescriber
- Strensiq injection sites should be rotated among the abdomen, thigh, deltoid, and buttocks; do not inject into skin that is red, swollen, or inflamed
- Strensiq vials should be removed from the refrigerator 15–30 minutes before use to reach room temperature; do not heat in a microwave or hot water
- Strensiq vials are single-use only — discard any unused medication after each injection
Oral solution
📊 Asfotase Alfa across the U.S. market
How Asfotase Alfa appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Asfotase Alfa is used
A general measure of how commonly Asfotase Alfa is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Asfotase Alfa is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Asfotase Alfa prescribed? Of the 1,596 medications we measure, Asfotase Alfa ranks #1,241 by Medicaid prescriptions — more than 22% of them.
Utilization by Asfotase Alfa product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
0.8 ML asfotase alfa 100 MG/ML Injection Most dispensed
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1720278
1 ML asfotase alfa 40 MG/ML Injection
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1720275
0.7 ML asfotase alfa 40 MG/ML Injection
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1720271
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Asfotase Alfa, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 3 of 6 listed Asfotase Alfa NDCs with Medicaid activity.
🔍 Compare Asfotase Alfa products
A representative set of FDA-listed product records for Asfotase Alfa — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Injection | ||||
| 18 mg/0.45 mL | Subcutaneous | Alexion Pharmaceuticals, Inc. × 3 listings | BLA | View NDC → |
| 28 mg/0.7 mL | Subcutaneous | Alexion Pharmaceuticals, Inc. × 3 listings | BLA | View NDC → |
| 40 mg/mL | Subcutaneous | Alexion Pharmaceuticals, Inc. × 3 listings | BLA | View NDC → |
| 80 mg/0.8 mL | Subcutaneous | Alexion Pharmaceuticals, Inc. × 3 listings | BLA | View NDC → |
| 💊Oral solution | ||||
| 107 mg/mL | — | Lonza Biologics Inc. | DRUG FOR FURTHER PROCESSING | View NDC → |
Showing 13 of 13 products — FDA National Drug Code Directory. See every product, package size and price: browse all 13 Asfotase Alfa NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Asfotase Alfa — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Asfotase Alfa in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Asfotase Alfa went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 1720259 1 dose form · 4 strengths
-
Dose form (SCDF) Injection RxCUI 1720262In current FDA listingsClinical drug / strength (SCD) 0.45 ML asfotase alfa 40 MG/MLRxCUI 17202630.7 ML asfotase alfa 40 MG/MLRxCUI 17202710.8 ML asfotase alfa 100 MG/MLRxCUI 17202781 ML asfotase alfa 40 MG/MLRxCUI 1720275
Look up RxCUI 1720259 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Asfotase Alfa is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Asfotase Alfa belongs to the Tissue-nonspecific Alkaline Phosphatase class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Alexion Pharmaceuticals, Inc. is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.