Generic Name

Omnitrope®

Mechanism

Omnitrope binds to the somatotropic receptor (GHR) on target tissues, triggering Janus kinase‑2 (JAK2) activation and subsequent phosphorylation of the insulin‑like growth factor‑1 (IGF‑1) signaling cascade.
• ↑GH‑induced synthesis of IGF‑1 in hepatocytes and peripheral tissues.
• IGF‑1 mediates mitogenic and anabolic effects: ↑cartilage growth, bone mineral accrual, muscle protein synthesis.
• Negative feedback regulates endogenous GH secretion via circulating IGF‑1 levels.

Pharmacokinetics

Indications

• Growth hormone deficiency (short‑stature) in pediatric and adult patients.
• Turner syndrome (short stature).
• Chronic kidney disease‑associated short stature (≥ 2 years).
• Idiopathic short stature (age‑adjusted height <‑2 SD).
• Prader‑Willi syndrome (growth delay).
• Relapsed growth hormone‑pretreated infants (≥ 120 days).
• Adult growth hormone deficiency (symptomatic).

Contraindications

• Severe hepatic diseases (elevated AST/ALT >5× ULN).
• Known hypersensitivity to any component.
• Intra‑uterine growth restriction patients not on GH therapy.
• Lactation: not recommended due to lack of safety data.
• Uncontrolled diabetes mellitus: potential for worsened glycemic control.
• Active malignancy: GH may stimulate tumor growth; use with extreme caution.

Dosing

• Route: Subcutaneous injection once daily, preferably at the same time each day.
• Initial Pediatric Dose: 0.025–0.05 mg/kg/day (max 0.05 mg/kg).
• Titration: Incrementally increase by 0.005–0.01 mg/kg weekly, guided by IGF‑1 levels and growth velocity.
• Adult Dose: 0.2 mg/day (adjust as needed).
• Administration Tip: Rotate injection sites (abdomen, thigh, upper arm) to prevent lipodystrophy.
• Reconstitution: Combine 10 mg vial with 1 mL preservative‑free diluent; use within 24 h if refrigerated (≤ 4 °C).

Adverse Effects

Monitoring

• IGF‑1 Levels: at baseline, 3–4 weeks, then monthly; target 0–2 SD above age‑matched mean.
• Growth Velocity: recorded every visit (≥ 6 weeks).
• Body Composition: baseline and every 6 months (DEXA or BIA).
• Blood Glucose / HbA1c: baseline and every 3 months; more frequent if symptomatic.
• Blood Pressure & Weight: at each appointment.
• Headache & Edema: document severity and duration.
• Serum Chemistry: ALT/AST and renal function yearly.
• MRI (if clinically indicated): suspected increased intracranial pressure.

Clinical Pearls

• IGF‑1 is the gold‑standard surrogate; a level > 2 SD correlates with an excessive GH dose and ↑ adverse‑effect risk.
• Start low, go slow: in young children, increasing by 0.01 mg/kg/week minimizes the risk of carpal tunnel syndrome.
• Use a dedicated pen: pens with built‑in volume controls reduce dosing errors and improve adherence.
• Co‑administration with Dexamethasone: glucocorticoids blunt IGF‑1 response—re‑titrate GH once steroid taper ends.
• Adolescent catch‑up: maximal benefit occurs if therapy continues through puberty; switching to puberty‑specific formulations may improve compliance.
• Safety in pregnancy: GH therapy is usually halted once conception is confirmed; no teratogenic data exist.
• Patient education: emphasize rotating injection sites and storing the drug refrigerated; do not freeze.

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• References

1. FDA prescribing information, Omnitrope® (Pfizer).

2. European Medicines Agency (EMA) – Product Information.

3. Egan, M. et al. “Growth hormone therapy in the pediatric population.” *Pediatrics* 2021.

4. National Institute for Health and Care Excellence (NICE) guideline on GH therapy, 2023.

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