# Genryzon Prescribing Guide > Bedside prescribing reference for Genryzon (somatrogon, Pfizer India) — the once-weekly long-acting growth hormone for paediatric growth hormone deficiency. Use when a clinician asks how to start Genryzon, how to dose somatrogon in a child, how to switch a child from daily growth hormone to weekly somatrogon, how to inject the Genryzon pen, missed-dose rule for somatrogon, when to stop somatrogon, or needs a monograph-level prescribing decision for a paediatric GHD patient. Applies to children and adolescents ≥3 years of age. Grounded in the Pfizer India Product Monograph (Genryzon LPD, 2022 — PfLEET 2022-0081166). - Skill: `dromlakhani/genryzon-prescribing-guide` (Agent Skill) - Install (CLI): `npx skillmds@latest add dromlakhani/genryzon-prescribing-guide` - Raw SKILL.md: https://api.skillmd.com/api/skills/dromlakhani/genryzon-prescribing-guide/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Marketing & Growth - Author: dromlakhani (https://skillmd.com/u/dromlakhani) - Updated: 2026-09-08 - Page: https://skillmd.com/skills/dromlakhani/genryzon-prescribing-guide --- # Genryzon (Somatrogon) Prescribing Guide Once-weekly long-acting recombinant human growth hormone for paediatric GHD. Initiated and monitored by a paediatric endocrinologist. --- ## Step 1 — Confirm the patient qualifies Genryzon is indicated when **ALL** of these are true: - Child or adolescent **≥3 years** of age - Confirmed **growth disturbance due to insufficient growth hormone secretion** (paediatric GHD) by an endocrinologist - **Open epiphyses** (do not use for growth if plates are closed) **Do NOT use** if any of: - Active tumour (intracranial tumour must be inactive AND antitumour therapy complete before starting) - Acute critical illness — post open-heart surgery, abdominal surgery, multiple trauma, acute respiratory failure - Prader-Willi syndrome **without** confirmed GHD (sudden death reports in PWS + severe obesity / airway obstruction / sleep apnoea / respiratory infection) - Hypersensitivity to somatrogon or excipients (m-cresol, poloxamer 188, L-histidine, sodium chloride, citric acid, trisodium citrate) - Child <3 years — safety/efficacy not established - Pregnancy, or renal/hepatic impairment (no data) --- ## Step 2 — Pretreatment work-up (do BEFORE first dose) - **Thyroid function** — treat any pre-existing hypothyroidism first (hypothyroidism blunts the GH response) - **Adrenal function** — GH may unmask central hypoadrenalism; if on glucocorticoid replacement, plan to review dose after starting - **Glucose tolerance** — baseline FPG ± HbA1c; GH reduces insulin sensitivity - **Fundoscopy** — baseline, for later comparison if benign intracranial hypertension is suspected - **Tumour clearance** — confirm intracranial tumour inactive; antitumour therapy complete - **Auxology + bone age** — baseline height, weight, height velocity, bone age --- ## Step 3 — Prescribe the starting dose **Standard dose: 0.66 mg/kg body weight, subcutaneous, ONCE WEEKLY.** Choose pen strength by body weight: | Body weight (weekly dose 0.66 mg/kg) | Pen to use | Increment | |---|---|---| | Up to ~18 kg (dose ≤12 mg) | **24 mg / 1.2 mL pen** (0.2–12 mg range) | 0.2 mg | | ~18–45 kg (dose 12–30 mg) | **60 mg / 1.2 mL pen** (0.5–30 mg range) | 0.5 mg | | **>45 kg (dose >30 mg)** | **60 mg pen — split into TWO injections at DIFFERENT sites** | 0.5 mg | Round the calculated dose to the nearest available increment. --- ## Step 4 — Administer - **Route:** subcutaneous only - **Sites:** abdomen · thighs · buttocks · upper arms — **rotate at every dose** - **Caregiver required** for injections into upper arms and buttocks - **Timing:** same day each week, **any time of day** - **If >1 injection needed** to deliver the full dose (i.e. >30 mg) → each injection at a **different site** - **Train patient + caregiver** in pen technique before self-administration --- ## Step 5 — Handle switches and calendar changes **Switching from daily GH → weekly somatrogon:** Start weekly somatrogon at **0.66 mg/kg/week on the day AFTER the last daily injection.** **Missed dose:** - **Within 3 days** of the scheduled dose → give ASAP, then resume the usual weekly schedule - **More than 3 days late** → **skip that dose**, give the next dose on the regularly scheduled day **Changing the weekly dosing day:** Allowed, provided **at least 3 days** between two consecutive doses. Then continue weekly on the new day. --- ## Step 6 — Monitor and titrate **Follow-up interval:** every **6–12 months** (more frequent during puberty). At each visit: - Auxology: height, weight, growth velocity - Biochemistry: **serum IGF-1** (see rule below), TSH, free T4, fasting glucose, HbA1c if diabetic risk - Pubertal status (Tanner stage) - Bone age (annually or as indicated) - Fundoscopy if suspicious symptoms **IGF-1 titration rule (critical — commonly done wrong):** - **Always draw the IGF-1 sample 4 days after the prior weekly dose** — otherwise the level is unrepresentative - **Target: IGF-1 SDS between −2 and +2** (aim close to 0) - **If IGF-1 SDS is >2 above the mean for age and sex → REDUCE the somatrogon dose by 15%** - More than one 15% reduction may be needed — reassess after each **Female patients on oral estrogen:** oral estrogen ↓ IGF-1 response to GH → a **higher somatrogon dose** may be needed to hit target IGF-1. Re-check IGF-1 if oral estrogen is started or stopped. --- ## Step 7 — When to STOP treatment Discontinue Genryzon when **ANY** of the following: - Evidence of **epiphyseal closure** - Achievement of final or near-final height — annualised **height velocity <2 cm/year** - **Bone age >14 years in girls** OR **>16 years in boys** --- ## Guardrails - **Do not start until the pretreatment work-up (Step 2) is complete** — starting somatrogon in an untreated hypothyroid child wastes therapy; starting in unrecognised central hypoadrenalism risks adrenal crisis when glucocorticoid replacement is unmasked - **IGF-1 timing matters** — 4 days post-dose. A sample taken 1 or 6 days post-dose misleads titration - **Split doses >30 mg into two injections at different sites** — do not deliver as a single injection - **Watch for these red flags during treatment** and act on them: - Severe abdominal pain → pancreatitis workup - Limp or hip/knee pain → slipped capital femoral epiphysis - Papilloedema, persistent headache, vision changes → benign intracranial hypertension → temporarily hold somatrogon, fundoscopy - Injection-site myalgia or disproportionate pain → myositis (m-cresol excipient); switch to a metacresol-free GH - New or recurrent neoplasm — especially childhood cancer survivors with prior cranial radiation (meningioma risk) - Progression of scoliosis - **Glucocorticoids** — concurrent glucocorticoid can inhibit growth response; ACTH-deficient children on replacement need their glucocorticoid dose reviewed. Somatrogon may also unmask previously undiagnosed central hypoadrenalism - **Diabetes** — GH ↓ insulin sensitivity. Patients on insulin or OADs may need dose ↑ after starting; monitor glucose more closely - **Thyroxine** — GH ↑ T4→T3 conversion, may unmask hypothyroidism; check TFTs at each review and replace if indicated - **CYP3A4 substrates** (sex steroids, corticosteroids, anticonvulsants, ciclosporin) — somatrogon may ↑ their clearance and lower their levels - **Do NOT use** in Prader-Willi syndrome unless the child also has documented GHD — sudden death has been reported in PWS on GH with severe obesity, airway obstruction, sleep apnoea, or respiratory infection - **Note the batch number** in the patient record (biological product traceability) --- ## Source Pfizer Products India Pvt. Ltd. **GENRYZON® (Somatrogon) Solution for Injection in Pre-filled Pen — Prescribing Information (India).** LPD version 2022-0081166 (PfLEET 2022-0081166). 40 pages.