GENOTROPIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GENOTROPIN (GENOTROPIN).

How it works

Recombinant human growth hormone (somatropin) binds to growth hormone receptors, activating JAK2/STAT5 signaling pathway, stimulating IGF-1 production and promoting linear growth, protein synthesis, and lipolysis.

What the body does with it

Metabolism	Primarily metabolized in the liver and kidneys via proteolytic degradation; not significantly metabolized by CYP450 enzymes.
Excretion	Renal (glomerular filtration and tubular reabsorption); approximately 70% of the administered dose is recovered in urine, primarily as intact hormone.
Half-life	Subcutaneous: 3.9 hours (range 2.3–6.1 hours). Clinical context: supports daily dosing; residual GH activity may extend due to reversible binding to GHBP.
Protein binding	Approximately 50–60% bound to growth hormone binding protein (GHBP); low-affinity binding to alpha-2-macroglobulin also occurs.
Volume of Distribution	Subcutaneous: approximately 0.07 L/kg. Clinical meaning: low Vd indicates limited distribution outside vascular and extracellular spaces.
Bioavailability	Subcutaneous: approximately 80% (range 70–90%) compared to intravenous administration.
Onset of Action	Subcutaneous: IGF-1 levels increase measurably within 4–6 hours; clinical growth effects require weeks to months of therapy.
Duration of Action	Subcutaneous: GH levels decline to baseline within 12–24 hours; growth stimulation requires daily administration for sustained effect.

Classification & Brands

Action Class

Somatostatin analogues

Dosing & administration

0.2 mg (0.6 IU) subcutaneously once daily; titrate based on clinical response and IGF-1 levels. Maximum dose: 0.8 mg (2.4 IU) daily.

Dosage form	INJECTABLE
Renal impairment	eGFR <30 mL/min: contraindicated. eGFR 30-60 mL/min: reduce dose by 50%. No adjustment for eGFR >60 mL/min.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 25%. Child-Pugh C: contraindicated.
Pediatric use	0.16-0.24 mg/kg subcutaneously per week, divided into 6-7 daily doses. Typical starting dose: 0.025-0.035 mg/kg daily. Adjust based on growth velocity and IGF-1 levels.
Geriatric use	Start at 0.1 mg subcutaneously three times per week; titrate slowly. Monitor for fluid retention and joint pain. Lower doses recommended due to increased risk of adverse events.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for GENOTROPIN (GENOTROPIN).

Breastfeeding	Not recommended during breastfeeding. It is unknown if somatropin is excreted in human milk. Somatropin is a large peptide (22 kDa) likely degraded in infant GI tract, but systemic absorption may occur. Risk cannot be excluded, especially for infants with growth hormone deficiency.
Teratogenic Risk	Somatropin (GENOTROPIN) is not recommended during pregnancy. No adequate human studies exist; animal studies show no teratogenic effects at doses up to 33 times the human dose. However, somatropin may affect glucose tolerance and could theoretically impact fetal growth. Use only if clearly needed and potential benefit justifies risk to fetus.

Warnings & precautions

■ FDA Black Box Warning

Increased risk of mortality in patients with acute critical illness due to complications following open heart surgery, abdominal surgery, or multiple accidental trauma. Also contraindicated in children with PWS who are severely obese or have severe respiratory impairment.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Patients with acute critical illness (open heart, abdominal surgery, multiple trauma, respiratory failure)","Pediatric patients with PWS who are severely obese or have severe respiratory impairment","Active malignancy","Diabetic retinopathy","Hypersensitivity to somatropin or any excipients"]

Clinical Precautions

Precautions

["Increased risk of benign intracranial hypertension (pseudotumor cerebri)","Slipped capital femoral epiphysis in pediatric patients","Progression of scoliosis","Pancreatitis","Glucose intolerance and diabetes mellitus","Increased risk of malignancy in patients with known neoplasms","Fluid retention and edema","Hypoadrenalism in patients with central GHD","Hypothyroidism","Respiratory compromise in PWS patients"]

Clinical Tips & Counseling

Drug interactions

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GENOTROPIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GENOTROPIN (GENOTROPIN).

How it works

What the body does with it

Metabolism	Primarily metabolized in the liver and kidneys via proteolytic degradation; not significantly metabolized by CYP450 enzymes.
Excretion	Renal (glomerular filtration and tubular reabsorption); approximately 70% of the administered dose is recovered in urine, primarily as intact hormone.
Half-life	Subcutaneous: 3.9 hours (range 2.3–6.1 hours). Clinical context: supports daily dosing; residual GH activity may extend due to reversible binding to GHBP.
Protein binding	Approximately 50–60% bound to growth hormone binding protein (GHBP); low-affinity binding to alpha-2-macroglobulin also occurs.
Volume of Distribution	Subcutaneous: approximately 0.07 L/kg. Clinical meaning: low Vd indicates limited distribution outside vascular and extracellular spaces.
Bioavailability	Subcutaneous: approximately 80% (range 70–90%) compared to intravenous administration.
Onset of Action	Subcutaneous: IGF-1 levels increase measurably within 4–6 hours; clinical growth effects require weeks to months of therapy.
Duration of Action	Subcutaneous: GH levels decline to baseline within 12–24 hours; growth stimulation requires daily administration for sustained effect.

Classification & Brands

Action Class

Somatostatin analogues

Dosing & administration

0.2 mg (0.6 IU) subcutaneously once daily; titrate based on clinical response and IGF-1 levels. Maximum dose: 0.8 mg (2.4 IU) daily.

Dosage form	INJECTABLE
Renal impairment	eGFR <30 mL/min: contraindicated. eGFR 30-60 mL/min: reduce dose by 50%. No adjustment for eGFR >60 mL/min.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 25%. Child-Pugh C: contraindicated.
Pediatric use	0.16-0.24 mg/kg subcutaneously per week, divided into 6-7 daily doses. Typical starting dose: 0.025-0.035 mg/kg daily. Adjust based on growth velocity and IGF-1 levels.
Geriatric use	Start at 0.1 mg subcutaneously three times per week; titrate slowly. Monitor for fluid retention and joint pain. Lower doses recommended due to increased risk of adverse events.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for GENOTROPIN (GENOTROPIN).

Breastfeeding	Not recommended during breastfeeding. It is unknown if somatropin is excreted in human milk. Somatropin is a large peptide (22 kDa) likely degraded in infant GI tract, but systemic absorption may occur. Risk cannot be excluded, especially for infants with growth hormone deficiency.
Teratogenic Risk	Somatropin (GENOTROPIN) is not recommended during pregnancy. No adequate human studies exist; animal studies show no teratogenic effects at doses up to 33 times the human dose. However, somatropin may affect glucose tolerance and could theoretically impact fetal growth. Use only if clearly needed and potential benefit justifies risk to fetus.