Asfotase Alfa

Source: UK SPC (eMC) §4.2 for Strensiq 100 mg/ml solution for injection (https://www.medicines.org.uk/emc/product/7991/smpc). VERBATIM: 'Recommended dosage regimen of asfotase alfa is 2 mg/kg of body weight administered subcutaneously three times per week, or a dosage regimen of 1 mg/kg of body weight administered subcutaneously six times per week. Maximum recommended dose of asfotase alfa is 6 mg/kg/week.' The SPC contains a per-body-weight dosing chart giving the exact dose in mg, the volume in ml and the vial type for each schedule, running from 3 kg to 100 kg (e.g. 20 kg = 40 mg / 1.00 ml three times weekly, or 20 mg / 0.50 ml six times weekly; 60 kg = 60 mg / 0.60 ml six times weekly) — use the SPC chart itself when dispensing, it was not reproduced in full here. INITIATION: treatment should be initiated by a physician experienced in the management of patients with metabolic or bone disorders. MISSED DOSE: if a dose is missed, a double dose should not be injected to make up for it. ADULT PATIENTS: pharmacokinetics, pharmacodynamics and safety have been studied in patients with hypophosphatasia over 18 years old; 'Dose adjustment is not needed in adult patients with paediatric-onset hypophosphatasia (HPP)'. NOTE — the SPC fetched gives no separate adult-onset HPP regimen; do not carry over any previously published adult-onset dose without a source. ELDERLY: safety and efficacy in elderly patients have not been established and no specific dose regimen can be recommended. HEPATIC IMPAIRMENT: safety and efficacy have not been evaluated and no specific dose regimen can be recommended. ADMINISTRATION: use sterile disposable syringes and injection needles of small enough volume that the prescribed dose can be withdrawn with reasonable accuracy; rotate injection sites and monitor them carefully for signs of potential reactions; patients can self-inject only if properly trained. §4.5 interactions was not present in the fetched bundle.

The SPC states a single weight-based regimen that applies across ages — Strensiq is indicated in paediatric-onset hypophosphatasia and the §4.2 dosing chart starts at a body weight of 3 kg. 2 mg/kg subcutaneously three times per week, or 1 mg/kg subcutaneously six times per week; maximum recommended dose 6 mg/kg/week. Maximum volume per injection 1 ml (give multiple injections at the same time if more is required). No separate paediatric dose reduction or age threshold is stated in the fetched §4.2.