Strensiq Dosage

Generic name: ASFOTASE ALFA 18mg in 0.45mL
Dosage form: injection
Drug class: Miscellaneous metabolic agents

Medically reviewed by Drugs.com. Last updated on Mar 14, 2023.

Dosage for Perinatal/Infantile-Onset HPP

The recommended dosage regimen of STRENSIQ for the treatment of perinatal/infantile-onset HPP is 6 mg/kg per week administered subcutaneously as either:

2 mg/kg three times per week, or
1 mg/kg six times per week. Injection site reactions may limit the tolerability of the six times per week regimen [see Adverse Reactions (6.1)].

The dose of STRENSIQ may be increased for lack of efficacy (e.g., no improvement in respiratory status, growth, or radiographic findings) up to 9 mg/kg per week administered subcutaneously as 3 mg/kg three times per week.

Dosage for Juvenile-Onset HPP

The recommended dosage regimen of STRENSIQ for the treatment of juvenile-onset HPP is 6 mg/kg per week administered subcutaneously as either:

2 mg/kg three times per week, or
1 mg/kg six times per week. Injection site reactions may limit the tolerability of the six times per week regimen [see Adverse Reactions (6.1)].

Preparation and Weight-Based Dosing Tables

Caution: Do not use the 80 mg/0.8 mL vial of STRENSIQ in pediatric patients weighing less than 40 kg because the systemic exposure of asfotase alfa achieved with the 80 mg/0.8 mL vial (higher concentration) is lower than that achieved with the other strength vials (lower concentration). A lower exposure may not be adequate for this subgroup of patients [see Dosage Forms and Strengths (3), Clinical Pharmacology (12.3)].

1.

Determine the total weekly volume needed for the prescribed dosage based on the patient's weight and recommended dosage. Follow these steps to determine the patient dose.

: Total weekly dose (mg) = patient's weight (kg) × prescribed dose (mg/kg/week)
: Total injection volume (mL) per week = Total dose (mg/week) divided by the STRENSIQ concentration (40 mg/mL or 100 mg/mL). Note product concentrations are: 40 mg/mL (vial strengths 18 mg/0.45 mL, 28 mg/0.7 mL, 40 mg/mL) or 100 mg/mL (vial strength 80 mg/0.8 mL).
: Round total injection volume to the nearest hundredth of a mL
: Total number of vials per week = Total injection volume divided by vial volume (mL)

2.

Determine the number of injection days per week (three or six per week).

3.

Determine dose per injection day. Patient weights should be rounded to the nearest kilogram when determining dose. Use the following tables for guidance, for patients administering 2 mg/kg three times per week (Table 1), 1 mg/kg six times per week (Table 2) and for dose escalations to 3 mg/kg three times per week, recommended only for patients with perinatal/infantile-onset HPP [see Dosage and Administration (2.1)] (Table 3).

Table 1: Weight-Based Dosing for Administration of 2 mg/kg Three Times per Week
Body Weight (kg)*	Dose to Inject	Volume to Inject	Vial Configuration
* Do not use the 80 mg/0.8 mL vial of STRENSIQ in pediatric patients weighing less than 40 kg [see Clinical Pharmacology (12.3)]. † When preparing a volume for injection greater than 1 mL, split the volume equally between two syringes, and administer two injections. When administering the two injections, use two separate injection sites.
3	6 mg	0.15 mL	18 mg/0.45 mL
4	8 mg	0.2 mL	18 mg/0.45 mL
5	10 mg	0.25 mL	18 mg/0.45 mL
6	12 mg	0.3 mL	18 mg/0.45 mL
7	14 mg	0.35 mL	18 mg/0.45 mL
8	16 mg	0.4 mL	18 mg/0.45 mL
9	18 mg	0.45 mL	18 mg/0.45 mL
10	20 mg	0.5 mL	28 mg/0.7 mL
15	30 mg	0.75 mL	40 mg/1 mL
20	40 mg	1 mL	40 mg/1 mL
25	50 mg	1.25 mL	Two 28 mg/0.7 mL vials
30	60 mg	1.5 mL	Two 40 mg/1 mL vials
35	70 mg	1.75 mL	Two 40 mg/1 mL vials
40	80 mg	0.8 mL	80 mg/0.8 mL
50	100 mg	1 mL	Two 80 mg/0.8 mL vials
60	120 mg	1.2 mL†	Two 80 mg/0.8 mL vials
70	140 mg	1.4 mL†	Two 80 mg/0.8 mL vials
80	160 mg	1.6 mL†	Two 80 mg/0.8 mL vials

Table 2: Weight-Based Dosing for Administration of 1 mg/kg Six Times per Week
Body Weight (kg)*	Dose to Inject	Volume to Inject	Vial Configuration
* Do not use the 80 mg/0.8 mL vial of STRENSIQ in pediatric patients weighing less than 40 kg [see Clinical Pharmacology (12.3)].
3	3 mg	0.08 mL	18 mg/0.45 mL
4	4 mg	0.1 mL	18 mg/0.45 mL
5	5 mg	0.13 mL	18 mg/0.45 mL
6	6 mg	0.15 mL	18 mg/0.45 mL
7	7 mg	0.18 mL	18 mg/0.45 mL
8	8 mg	0.2 mL	18 mg/0.45 mL
9	9 mg	0.23 mL	18 mg/0.45 mL
10	10 mg	0.25 mL	18 mg/0.45 mL
15	15 mg	0.38 mL	18 mg/0.45 mL
20	20 mg	0.5 mL	28 mg/0.7 mL
25	25 mg	0.63 mL	28 mg/0.7 mL
30	30 mg	0.75 mL	40 mg/1 mL
35	35 mg	0.88 mL	40 mg/1 mL
40	40 mg	1 mL	40 mg/1 mL
50	50 mg	0.5 mL	80 mg/0.8 mL
60	60 mg	0.6 mL	80 mg/0.8 mL
70	70 mg	0.7 mL	80 mg/0.8 mL
80	80 mg	0.8 mL	80 mg/0.8 mL
90	90 mg	0.9 mL	Two 80 mg/0.8 mL vials
100	100 mg	1 mL	Two 80 mg/0.8 mL vials

Table 3: Weight-Based Dosing for Administration of 3 mg/kg Three Times per Week – Only for Perinatal/Infantile-Onset HPP*
Body Weight (kg)†	Dose to Inject	Volume to Inject	Vial Configuration
* A regimen of 3 mg/kg three times per week is recommended only for patients with perinatal/infantile-onset HPP [see Dosage and Administration (2.1)] † Do not use the 80 mg/0.8 mL vial of STRENSIQ in pediatric patients weighing less than 40 kg [see Clinical Pharmacology (12.3)]. ‡ When preparing a volume for injection greater than 1 mL, split the volume equally between two syringes, and administer two injections. When administering the two injections, use two separate injection sites.
3	9 mg	0.23 mL	18 mg/0.45 mL
4	12 mg	0.3 mL	18 mg/0.45 mL
5	15 mg	0.38 mL	18 mg/0.45 mL
6	18 mg	0.45 mL	18 mg/0.45 mL
7	21 mg	0.53 mL	28 mg/0.7 mL
8	24 mg	0.6 mL	28 mg/0.7 mL
9	27 mg	0.68 mL	28 mg/0.7 mL
10	30 mg	0.75 mL	40 mg/1 mL
15	45 mg	1.13 mL‡	Two 28 mg/0.7 mL vials
20	60 mg	1.5 mL‡	Two 40 mg/1 mL vials
25	75 mg	1.88 mL‡	Two 40 mg/1 mL vials

4.: Take the unopened STRENSIQ vial(s) out of the refrigerator 15 to 30 minutes before injecting to allow the liquid to reach room temperature.
Do not warm STRENSIQ in any other way (for example, do not warm it in a microwave or in hot water).
5.: Inspect the solution in the vial(s) for particulate matter and discoloration. STRENSIQ is supplied as a clear, slightly opalescent or opalescent, colorless to slightly yellow aqueous solution; a few small translucent or white particles may be present. Discard any vial(s) not consistent with this appearance.
6.: Assemble injection supplies. Administer STRENSIQ using sterile disposable 1 mL syringes and ½ inch injection needles, between 25 to 29 gauge are recommended. The use of two different gauge needles is recommended, a larger bore needle (e.g. 25 gauge) for withdrawal of the medication, and a smaller bore needle (e.g. 29 gauge) for the injection. For doses greater than 1 mL, the injection volume should be split equally between two 1 mL syringes. Always use a new syringe and needle for each injection.
7.: Remove vial cap, aseptically prepare the vial and insert the syringe into the vial to withdraw the prescribed dose for administration. Do not shake.
8.: Remove any air bubbles in the syringe and verify the correct dose.
9.: STRENSIQ vials are for one time use only. Discard any unused product.

Administration

STRENSIQ is for subcutaneous injection only.

When administering two injections, use two separate injection sites.
Administer STRENSIQ within 3 hours upon removal of the vial(s) from refrigeration.
Rotate the injection from among the following sites to reduce the risk of lipodystrophy: abdominal area, thigh, deltoid, or buttocks [see Warnings and Precautions (5.2), Adverse Reactions (6.1)].
Do NOT administer injections in areas that are reddened, inflamed, or swollen.
Inject STRENSIQ subcutaneously into the determined site and properly dispose of the syringe and the needle.