asfotase alfa


az-fo-tase al-fa

Trade Name(s)

  • Strensiq

Ther. Class.

none assigned

Pharm. Class.



Perinatal/infantile- and juvenile-onset hypophosphatasia (HPP).


As a recombinant form of tissue nonspecific alkaline phosphatase, it promotes bone mineralization.

Therapeutic Effect(s):

Improved survival in patients with perinatal/infantile-onset HPP; improved growth and mobility in patients with juvenile-onset HPP.


Absorption: 60% absorbed after SUBQ administration.

Distribution: Unknown.

Metabolism and Excretion: Unknown.

Half-life: 5 days.

TIME/ACTION PROFILE (reduction in plasma tissue nonspecific alkaline phosphatase substrates)

SUBQ6–12 wkunknownunknown


Contraindicated in:

  • None.

Use Cautiously in:

  • OB:   Safety not established in pregnancy;
  • Lactation:  Use while breastfeeding only if potential maternal benefit justifies potential risk to infant.

Adverse Reactions/Side Effects

EENT: ectopic calcification of eye

GU: ectopic calcification of kidney

Metabolic: lipodystrophy

Misc: HYPERSENSITIVITY REACTIONS (including anaphylaxis), injection site reactions

* CAPITALS indicate life-threatening.
Underline indicate most frequent.



None known.


Perinatal/Infantile-Onset HPP

SUBQ (Neonates and Infants): 2 mg/kg 3 times weekly  or  1 mg/kg 6 times weekly; if suboptimal response, may ↑ to 3 mg/kg 3 times weekly.

SUBQ (Children ≤16 yr): 2 mg/kg 3 times weekly or  1 mg/kg 6 times weekly.


Solution for injection: 18 mg/0.45 mL, 28 mg/0.7 mL, 40 mg/mL, 80 mg/0.8 mL


  • Assess for signs and symptoms of HPP (biochemical, medical history and radiographic evidence of HPP as well as presence of any of the following: rachitic chest deformity, vitamin B6-dependent seizures, or failure to thrive) prior to therapy.
  • Monitor for signs and symptoms of hypersensitivity reactions (difficulty breathing, nausea or vomiting, swelling around eyes, lips or tongue, hives, feeling faint, dizziness, itching of lips, tongue or throat). If symptoms severe, discontinue therapy, consider risks and benefits or resuming therapy. Monitor closely.
  • Obtain ophthalmalogic exams and renal ultrasounds and baseline and periodically during therapy to monitor for calcifications leading to visual changes and decreased renal function.

Lab Test Considerations:

Inform lab that asfotase alfa interferes with alkaline phosphatase testing. High serum alkaline phosphatase levels are expected and reflect circulating concentrations of asfotase alfa. Do not use alkaline phosphatase levels for clinical decisions.


  • SUBQ Prepare dose using 1 mL syringes and ½ inch needles, between 25 to 29 gauge. See manufacturer's guidelines for dose preparation. If >1 mL, split volume equally between 2 syringes, and administer 2 injections, in 2 separate sites. Remove air bubbles from syringe. Solution is clear, colorless to slightly yellow, opalescent or slightly opalescent, with few translucent or white particles; do not administer solution that are discolored or contain lumps or large particles. Do not shake vials. Pinch skin and inject at 90° angle; for patients with little fat, use 45° angle. Rotate sites between abdomen, upper arms, and upper legs to prevent lipodystrophy. Do not inject into areas that are hot, red, or swollen. Store in original carton in refrigerator and administer within 1 hr of removing from refrigerator; do not freeze. Protect from light.

Patient/Family Teaching

  • Explain purpose of medication to parents. Instruct in correct technique for administration, storage, and disposal of supplies.
  • Advise parents to monitor for signs of hypersensitivity reactions; if severe, take patient to nearest emergency department.
  • Advise parents to monitor for skin thickening or pits and injection sites. Rotate injection sites to prevent lipodystrophy.
  • Explain need for eye and kidney exams periodically during therapy to parents.
  • Advise parents to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
  • Encourage parents to enroll patient in the Hypophosphatasia (HPP) Registry to better understand HPP and monitor long term progress of patients. Participation is voluntary at

Evaluation/Desired Outcomes

  • Improved survival in patients with perinatal/infantile-onset HPP.
  • Improved growth and mobility in patients with juvenile-onset HPP.