Mastering the dose calculation, preparation operation, injection technique, and missed-dose management for Navepegritide is the key to ensuring smooth treatment.

I. Dose Determination and Adjustment Principles

1. Body weight‑driven dosing regimen

(1) Dose anchoring: The total weekly dose is calculated strictly based on the actual body weight on the day of administration; weigh before each injection and verify the corresponding dose.

(2) Dose range coverage: The regimen covers individualized needs from young children to adolescents across different body sizes, ensuring a matching dose for each weight bracket.

(3) Treatment discontinuation criteria: Once imaging or clinical confirmation of epiphyseal closure is obtained, indicating exhausted growth potential, administration should be stopped.

2. Regular weight monitoring and recalibration

(1) Dynamic adjustment rhythm: Children are in continuous growth and development, with rapid weight changes; re‑measure body weight regularly (e.g., every 1–3 months).

(2) Dose increase with weight gain: If weight increases beyond the current dose bracket, adjust upward to the dose corresponding to the new weight to avoid prolonged "relative underdosing".

(3) Physician‑led adjustments: All dose changes must be calculated and confirmed by the prescribing physician; family members must not alter the dose based on memory or estimation.

3. Timing for switching from a daily CNP regimen

Seamless transition: If a daily C‑type natriuretic peptide analogue was previously used, initiate the first weekly injection on the day after the last daily injection, avoiding a treatment gap.

II. Preparation Operation Standards and Key Details

1. Before reconstitution

(1) Bring to room temperature: After removing the vial and diluent syringe from refrigeration, let stand for about 30 minutes to reach room temperature, reducing cold stimulation and incomplete dissolution.

(2) Inspect appearance: Check that the lyophilized powder in the vial is intact and undamaged; the diluent should be a clear liquid, free from turbidity or particles.

2. Key steps for reconstitution

(1) Inject diluent: Attach the preparation needle to the diluent syringe and inject the entire volume of diluent into the vial.

(2) Shaking method: Shake vigorously vertically up and down for 15 seconds; do not swirl or roll to avoid foaming or uneven distribution of the active ingredient.

(3) Let stand: After shaking, let stand at room temperature for 5 minutes to allow the solution to stabilize; the solution should be clear and colorless, with a few small bubbles being normal.

3. Aspiration of the drug solution and syringe preparation

(1) Correct aspiration: Replace with a new preparation needle, draw the prescribed volume of solution with the syringe, ensuring the needle tip is below the liquid surface to prevent drawing air.

(2) Priming: After drawing, push the plunger back to expel large bubbles and any dead space, ensuring the scale accurately corresponds to the prescribed volume; tiny bubbles may be ignored.

(3) Change to injection needle: After aspirating the drug solution, remove the preparation needle and replace it with a dedicated fine injection needle (30G) to reduce injection pain.

III. Injection Execution and Missed‑Dose Management Strategy

1. Permitted injection sites and rotation rules

(1) Self‑injection sites: Abdomen (at least 5 cm from the navel) and the anterolateral thigh.

(2) Assisted injection sites: If administered by a parent or caregiver, the outer upper quadrant of the buttock or the posterior upper arm may also be used.

(3) Strict rotation: Change the injection side and specific site each time to avoid repeated injection in the same area, which may cause subcutaneous induration or local reactions.

2. Single‑injection procedure

(1) Needle angle: Insert at a 45‑degree angle subcutaneously, inject slowly and steadily; avoid too rapid injection to prevent pain or tissue damage.

(2) Dose splitting: When the calculated single volume exceeds 1 mL, use two separate kits and divide the total dose into two injections, with different injection sites for each.

(3) Post‑injection disposal: Discard all used needles, syringes, and any residual solution into a dedicated sharps container; do not recap the needle.

3. Missed dose and schedule adjustment rules

(1) Catch‑up window: If a dose is missed, it can be given any time within 2 days; after a catch‑up dose, the next dose remains on the original fixed day.

(2) Beyond the window: If more than 2 days have passed since the scheduled dosing day, skip the missed dose and inject the normal dose on the next regular dosing day.

(3) Changing the dosing day: If you need to change the fixed weekly injection day, ensure at least 5 days between the old and new injection days to avoid two injections being too close.

(4) Minimum interval constraint: Any two injections should be at least 5 days apart to maintain a stable fluctuation range of blood drug concentration.