Your first 90 days
Your first 90 days on Strensiq for hypophosphatasia
What happens before the first fill, the days that matter, the label's rules and who to call, from the label, the drugmaker's own program and one insurer's written rules.
Most people starting Strensiq are babies and young children, so this page is written for parents, guardians and caregivers as much as for patients. Strensiq replaces the enzyme that people with HPP are missing, and it is given as a small shot under the skin several times a week. The first weeks are about learning the injection, measuring the right dose for your child's weight and knowing the signs of an allergic reaction. This page lays out those 3 months from the FDA label, Alexion's OneSource program and one insurer's written rules.
What has to happen before the first bottle ships
Strensiq has no REMS, so the first fill waits on lab and weight records, a prescription form sent to PANTHERx Rare and an insurance approval. These are the 7 things in the way, in order.
A check that Strensiq fits the diagnosis
The label approves Strensiq for HPP that began before birth, in infancy or in childhood.
- The prescriber confirms which form of HPP your child has and whether Strensiq fits.FDA label
Lab results and symptoms on paper
Alexion's prescription form asks for an alkaline phosphatase (ALP) result and a PLP or PEA result.
- It also asks for the signs and symptoms of HPP, both at onset and now.Prescription form
A current weight
Every Strensiq dose is worked out from body weight, and the prescription form asks for the current weight and the date it was taken.
- The label rounds weight to the nearest kilogram when setting the dose.Prescription form
An eye exam and a kidney ultrasound
People with HPP can build up calcium in the eyes and kidneys.
- The label recommends an eye exam and a kidney ultrasound before treatment starts, and from time to time after that.FDA label
The prescription form and insurance cards
The prescriber's office faxes Alexion's prescription form to PANTHERx Rare Pharmacy with copies of both sides of every insurance card.
- Alexion calls PANTHERx Rare the exclusive preferred specialty pharmacy for Strensiq.Prescription form
Enrolling in OneSource
For help with insurance and treatment logistics, OneSource needs its own enrollment form.
- Families can sign it online, or email or fax a paper copy.OneSource enrollment
The insurance approval
PANTHERx Rare checks your benefits, tells the office what the plan requires and ships once the prior authorization is approved.
- Alexion's guide suggests including at least 2 ALP results taken more than 30 days apart.Access guide
The days that matter
Counted from the first shot, with the paperwork before it, refills every 28 days and the weight changes that move the dose. Type your first-dose date and the tiles become real dates you can add to your calendar.
The tiles below count days from a first dose. Enter the date of yours, or the date you expect, and each tile becomes a real date on your calendar.
The date stays on your device. It is not sent to Trial Friend or anyone else. The calendar file works with Apple, Google and Outlook calendars.Prescription form and OneSource enrollment
The office faxes the prescription form with labs, weight and insurance cards to PANTHERx Rare.
- Families sign the OneSource enrollment form so a Case Manager can help with coverage.
Eye exam and kidney ultrasound
The label recommends an eye exam and a kidney ultrasound before Strensiq starts.
- These give a starting point for the checks repeated during treatment.
Prior authorization
PANTHERx Rare runs the benefits check and shares what the plan requires.
- Once the plan approves, the pharmacy schedules the first shipment.
The cold shipment arrives
PANTHERx Rare ships the vials along with needles and syringes.
- The vials go straight into the refrigerator in their original carton, away from light.
First shot, with a healthcare provider
The label says Strensiq is started under the supervision of a healthcare provider, because of the risk of a severe allergic reaction.
- Ask the care team whether training on preparing and giving the shot happens at this visit.
Next shot on the schedule
On 3 shots a week, the next one comes about 2 days later.
- The label asks you to use a different spot for each shot, rotating between belly, thighs, upper arms and buttocks.
One week in
Redness, swelling or itching where the shot went in is the most common side effect.
- The label says most of these reactions cleared within a week.
Refill every 28 days
Alexion's prescription form writes a 28-day supply with up to 11 refills.
- Ask PANTHERx Rare to confirm each shipment date before the last vials run out.
Refill every 28 days, number 2
Refill every 28 days, number 3
A new weight can mean a new dose
Because the dose follows weight, a growing child's dose and vial size change over time.
- Tell the office about weight changes so the prescription keeps up.
The label, revision by revision
The FDA lists which sections changed in each revision of a label. These are the revisions the current Strensiq label records, dated by the FDA, with a plain note on what each one meant for a patient. Older references and handouts can lag these by months.
Current label dated December 12, 2025, read from the FDA's label database today. FDA label
- December 2025
The current version of the label on DailyMed is dated December 12, 2025. Its highlights still read revised July 2024, and its Patient Information is also dated July 2024.FDA label
- July 2024
The label added a boxed warning for severe allergic reactions, including anaphylaxis. It also added the advice to start Strensiq under a healthcare provider's supervision and updated the allergy warning.FDA label
- June 2020
The FDA approved an efficacy supplement to the Strensiq application on June 12, 2020. The current Instructions for Use carry an approval date of June 2020.Drugs@FDA record
- October 2015
The FDA first approved Strensiq on October 23, 2015, for perinatal/infantile- and juvenile-onset HPP.Drugs@FDA record
How the label says to take it
The parts of the prescribing information and the patient leaflet that come up in the first 3 months, in plain words.
- The dose, by weight
The label's usual dose is 6mg/kg a week, measured by body weight.
- That is given as 2mg/kg 3 times a week, or 1mg/kg 6 times a week.FDA label
- A higher dose for some babies
For HPP that began before birth or in infancy, the label allows up to 9mg/kg a week if breathing, growth or X-rays are not improving.
- That dose is given as 3mg/kg 3 times a week.FDA label
- What a dose looks like
At 2mg/kg 3 times a week, a 6kg (about 13 pound) baby gets 12mg, which is 0.3mL from an 18mg vial.
- A 20kg (about 44 pound) child gets 40mg, which is 1mL from a 40mg vial.FDA label
- Two shots when the dose is over 1mL
When a dose is more than 1mL, the label says to split it equally between 2 syringes.
- The 2 shots then go into 2 different spots on the body.FDA label
- The 80mg vial is only for 40kg and up
The label says not to use the 80mg/0.8mL vial in children under 40kg (about 88 pounds).
- That vial gives about 25% less medicine to the body at the same dose.FDA label
- Warming the vial
The label says to take the vial out of the refrigerator 15 to 30 minutes before the shot.
- Never warm it in a microwave or hot water, and give it within 3 hours of removing it.FDA label
- Where the shot goes
The Instructions for Use list the belly, upper arms, upper legs or buttocks, and say not to use the buttocks for infants.
- The label says to skip any spot that is red, hot or swollen.FDA label
- One vial, one use
Each vial is used once, and anything left over is thrown away.
- A new syringe and needle are used for every shot, then go into a sharps container.FDA label
- Storage
Keep vials in the original carton in the refrigerator at 36 to 46 degrees Fahrenheit, protected from light.
- The label says never to freeze the vials and never to shake them.FDA label
- Tell every lab about Strensiq
Strensiq is itself an alkaline phosphatase, so ALP blood results run high and some lab tests can read wrong.
- The label asks you to tell lab staff that the patient takes Strensiq.FDA label
- If a dose is missed
The label and Instructions for Use do not say what to do after a missed shot.
- Ask the prescriber or PANTHERx Rare ahead of time what they want you to do.FDA label
- Pregnancy and breastfeeding
The label says there are no data on Strensiq in pregnancy or in breast milk.
- Tell the prescriber about a pregnancy, plans for one or breastfeeding.FDA label
What the label says to act on
The symptoms the label singles out, and what it tells patients and prescribers to do about each. If any of these happen, the label's instruction is the one to follow, with your care team.
Signs of a severe allergic reaction
The Patient Information lists trouble breathing, a choking feeling, swelling of the eyes, lips or tongue, dizziness, nausea or vomiting, fever and hives.
- It says to go to the nearest emergency room right away if these appear.FDA label
Allergic reactions can come late
The label says severe reactions have happened within minutes of a shot and also more than 1 year after starting.
- The warning signs matter for as long as treatment lasts.FDA label
Skin changes where the shots go
Redness, color change, pain, itching, swelling and hard lumps are common at shot sites.
- In the trials, these reactions affected 63% of patients and 90% of those with juvenile-onset HPP.FDA label
Thickened or dented skin after months
The label reports lumps or dents in the fat under the skin after several months of shots.
- It affected 28% of patients in the trials, and rotating sites is the label's advice.FDA label
HPP symptoms coming back
The body can make antibodies to Strensiq that make it work less well.
- The Patient Information says to tell the provider right away about worse breathing, walking, tiredness, bone pain, stiff joints or appetite loss.FDA label
Why the pharmacy or the insurer says no, and what fixes it
Most first-fill delays are one of these. Knowing which one tells you who to call.
- The prescription went to another pharmacyAlexion's prescription form goes to PANTHERx Rare, which Alexion calls the exclusive preferred specialty pharmacy for Strensiq. The office resends it there, which is a routing fix rather than a denial.Access Navigator
- The plan says the labs are missingAlexion's guide to common plan criteria lists low ALP and a raised PLP or PEA. It suggests sending at least 2 recent ALP results taken more than 30 days apart.PA criteria guide
- The plan says HPP began too lateCigna's policy, effective September 15, 2026, requires that the disease began before age 18. Adults with childhood-onset HPP need records showing when symptoms began.Cigna policy
- The prescriber is not a specialistCigna asks for a geneticist, an endocrinologist, a metabolic specialist or an HPP specialist to prescribe or consult. A consult note from one of them can meet this.Cigna policy
- The appeal was deniedAlexion's access guide lists a resubmission, a peer-to-peer review or a formal appeal. Alexion offers prescribers a sample appeal letter and a letter of medical necessity template.Access guide
- A copay you cannot payThe CoPay Program can bring eligible commercial plans to as little as $0, up to a yearly maximum that may vary. Medicare, Medicaid, TRICARE, VA and other government plans are excluded, and OneSource can point to outside help.CoPay terms
Cigna prior authorization policy, September 15, 2026
- Diagnosis supported by one of these: disease-causing ALPL gene changes on genetic testing, a low baseline serum alkaline phosphatase, or a raised enzyme substrate such as PLP, pyrophosphate or urine PEA, with documentation
- Current or past signs of HPP, such as skeletal problems, early tooth loss, muscle weakness, poor feeding, failure to thrive, breathing problems or vitamin B6-dependent seizures, or a parent or sibling with HPP
- Disease onset before age 18
- Prescribed by or with a geneticist, endocrinologist, metabolic disorder specialist or a physician who specializes in HPP
Approval length. A year at a time, with the same criteria at each review.
Cigna's policy IP0308 took effect September 15, 2026 after an August 2026 review with no criteria changes, and it cites the July 2024 Strensiq label. That matches the current label's text, so the policy does not predate it. Other plans set their own rules, and this one is an example. The federal employee plan, for example, asks for eye and kidney checks and improvement in growth and X-rays after the first year. Cigna policy
Who to call, and what they can do
The drugmaker's program handles most of the first-fill problems above. Charity funds and foundation help are on the help paying page.
- A free support program with a dedicated Case Manager who answers questions about HPP and Strensiq
- Help understanding insurance coverage for Strensiq and with financial concerns or gaps in coverage
- Support preparing for injections and help avoiding treatment gaps during insurance changes, travel or other life events OneSource team
- A CoPay Program for commercial insurance, as little as $0 up to a yearly maximum, not valid with Medicare, Medicaid, TRICARE, VA or other government plans CoPay terms
- For people with Medicare, Medicaid or other government plans, connection to third-party resources that may help with costs OneSource financial help
- Interpreters for families whose preferred language is not English OneSource enrollment
Details as the drugmaker publishes them. OneSource
Five questions for the pharmacist or the support line
- Has PANTHERx Rare received the prescription form, and is anything missing before you can ship?
- Which vial size will we get for my child's weight, and how many vials come in each shipment?
- Can you walk me through the dose in mL that I should draw up for each shot?
- The label does not say what to do after a missed shot, so what should we do if one is missed?
- My child's weight has changed, so who updates the dose and when does the new vial size start?
Questions people ask in the first weeks
How is the Strensiq dose worked out?
The label sets the dose by weight, usually 6mg/kg a week. That is given as 2mg/kg 3 times a week or 1mg/kg 6 times a week. The prescriber sets the regimen, and the label rounds weight to the nearest kilogram.
Why is the first Strensiq shot given with a provider?
The label has a boxed warning for severe allergic reactions, including anaphylaxis. It says to start Strensiq under the supervision of a healthcare provider with the right medical monitoring and support.
What are the signs of a serious allergic reaction to Strensiq?
The Patient Information lists trouble breathing, a choking feeling, swelling of the eyes, lips or tongue, dizziness, vomiting, fever, hives and itching. It says to go to the nearest emergency room right away.
Can we use the 80mg vial for a small child?
No, the label says not to use the 80mg/0.8mL vial in children under 40kg, about 88 pounds. That stronger vial gives about 25% less medicine to the body than the other vials at the same dose.
How do we store Strensiq at home?
The label says to keep vials in the original carton in the refrigerator at 36 to 46 degrees Fahrenheit, away from light. Never freeze or shake them, and give each shot within 3 hours of taking the vial out.
What checks are needed on Strensiq?
The label recommends an eye exam and a kidney ultrasound before treatment and from time to time during it. HPP itself raises the risk of calcium deposits in the eyes and kidneys.
Why does my child's ALP test look so high?
Strensiq is itself an alkaline phosphatase, so the label says high ALP results are expected and should not guide decisions. It asks families to tell lab staff, since some other tests can read wrong too.
Is there help paying for Strensiq?
Alexion OneSource runs a CoPay Program that can bring the cost to as little as $0 for eligible commercial plans. People with Medicare, Medicaid or other government plans are not eligible, and OneSource can connect them with outside resources.
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Sources
- STRENSIQ- asfotase alfa solution, prescribing information, Patient Information and Instructions for Use, highlights revised 7/2024, DailyMed version 18, Alexion Pharmaceuticals, via DailyMed, December 12, 2025.
- Drugs@FDA application record, BLA125513, STRENSIQ (asfotase alfa), submissions and approval dates, FDA, via openFDA, November 10, 2026.
- Alexion OneSource™ | STRENSIQ | About OneSource, Alexion Pharmaceuticals, November 10, 2026.
- Alexion OneSource™ | STRENSIQ | Fill Out a Start Form, Alexion Pharmaceuticals, November 10, 2026.
- Alexion OneSource™ | STRENSIQ | Financial Assistance, Alexion Pharmaceuticals, November 10, 2026.
- Alexion OneSource™ | STRENSIQ | Meet The Team, Alexion Pharmaceuticals, November 10, 2026.
- Alexion OneSource™ CoPay Program Terms and Conditions, US/ALL/1223 V1 12/2024, Alexion Pharmaceuticals, November 10, 2026.
- Alexion Access Navigator | Strensiq, Alexion Pharmaceuticals, November 10, 2026.
- STRENSIQ® (asfotase alfa) Prescription (Rx) Form for the Treatment of Pediatric-Onset Hypophosphatasia (HPP), US/STQ-H/0574 V1 07/2024, Alexion Pharmaceuticals, November 10, 2026.
- How to Access STRENSIQ, access and reimbursement guide, US/STQ-H/0475 V3 07/2024, Alexion Pharmaceuticals, November 10, 2026.
- A Guide to Common Prior Authorization (PA) Criteria for STRENSIQ® (asfotase alfa), US/STQ-H/0724 V1 07/2025, Alexion Pharmaceuticals, November 10, 2026.
- Sample Letter of Medical Necessity for STRENSIQ® (asfotase alfa), US/STQ-H/0196 V6 11/2025, Alexion Pharmaceuticals, November 10, 2026.
- Drug Coverage Policy IP0308, Enzyme Replacement Therapy, Strensiq, Cigna, September 15, 2026.
- Strensiq (asfotase alfa), pharmacy policy 5.30.015, Blue Cross and Blue Shield Federal Employee Program, April 1, 2025.
This page explains what the FDA label, the drugmaker's support program and an insurer policy say. It is not medical advice and does not tell anyone to start, stop or change a medicine. Dosing, test timing and restarts after a gap are decisions for the prescribing endocrinologist. Found an error? Use the report link in the footer and it will be checked against the source.