ZOMACTON

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ZOMACTON (ZOMACTON).

How it works

ZOMACTON is a recombinant human growth hormone that binds to growth hormone receptors on cell surfaces, activating intracellular signaling cascades (primarily JAK-STAT pathway) leading to increased IGF-1 production, which mediates growth and metabolic effects including linear growth, protein synthesis, and lipolysis.

What the body does with it

Metabolism	Growth hormone is metabolized in the liver and kidney via proteolysis; no specific CYP450 enzymes involved.
Excretion	Renal: nearly 100% of absorbed dose, mostly as intact hormone; negligible biliary/fecal elimination.
Half-life	Terminal elimination half-life: 2-3 hours after subcutaneous administration; clinically, this necessitates daily or more frequent dosing.
Protein binding	Approximately 30-40%, primarily bound to growth hormone binding protein (GHBP) and low-affinity binding proteins.
Volume of Distribution	0.07-0.1 L/kg, indicating limited extravascular distribution; primarily confined to plasma volume.
Bioavailability	Subcutaneous: 75-85%; intramuscular: 80-90%; intravenous: 100%.
Onset of Action	Subcutaneous: 2-4 hours; intravenous: 15-30 minutes; intramuscular: 2-4 hours.
Duration of Action	Subcutaneous: 12-24 hours; intravenous: 8-12 hours; clinical effect duration shorter than metabolic clearance.

Classification & Brands

Action Class

Growth hormone agonist

Dosing & administration

Intramuscular or subcutaneous injection: 0.1-0.3 mg/kg/day (up to 0.6 mg/kg/day) divided into 1-2 doses. Typical adult dose for growth hormone deficiency: 0.2 mg/kg/day subcutaneously.

Dosage form	INJECTABLE
Renal impairment	No specific guidelines. Somatropin may be used in patients with renal impairment; however, monitoring for fluid retention and electrolyte imbalances is advised. GFR-based dose reduction is not established.
Liver impairment	No specific Child-Pugh based adjustments. Caution in severe hepatic impairment due to potential for decreased clearance; monitor for adverse effects.
Pediatric use	Growth hormone deficiency: 0.025-0.05 mg/kg/day subcutaneously once daily; maximum 0.1 mg/kg/day. For Turner syndrome: 0.05 mg/kg/day. For chronic renal insufficiency: 0.045-0.05 mg/kg/day.
Geriatric use	Use lowest effective dose. May require lower doses due to age-related changes in metabolism and increased risk of adverse effects such as fluid retention, arthralgia, and glucose intolerance. Regular monitoring of IGF-1 levels recommended.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for ZOMACTON (ZOMACTON).

Breastfeeding	Excretion into human milk is unknown; somatropin is a large protein and likely degraded in infant GI tract. No M/P ratio reported. Caution; benefit should outweigh risk.
Teratogenic Risk	No well-controlled studies in pregnant women. Animal studies are inadequate or inconclusive. Somatropin is not recommended during pregnancy unless clearly needed. First trimester: limited data suggests no increased malformation risk; second/third trimester: theoretical risk of maternal glucose intolerance and fetal growth acceleration.

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, or those with acute respiratory failure. ZOMACTON should not be used for such conditions.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Acute critical illness (e.g., open heart surgery, abdominal surgery, multiple trauma, acute respiratory failure)","Active malignancy (except for certain specific indications)","Evidence of active progression of any underlying intracranial tumor","Diabetic retinopathy","Hypersensitivity to somatropin or any excipients","Children with closed epiphyses (for growth promotion)"]

Clinical Precautions

Precautions

["Risk of neoplasms (active malignancy)","Intracranial hypertension (pseudotumor cerebri)","Slipped capital femoral epiphysis","Pancreatitis","Glucose intolerance/diabetes mellitus","Fluid retention (edema, arthralgias)","Hypoadrenalism in patients with ACTH deficiency","Thyroid dysfunction (monitor thyroid function)","Progression of scoliosis","Lipoatrophy at injection site","Antibody formation to growth hormone"]

Clinical Tips & Counseling

Drug interactions

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ZOMACTON

Clinical safety rating: caution

Comprehensive clinical and safety monograph for ZOMACTON (ZOMACTON).

How it works

What the body does with it

Metabolism	Growth hormone is metabolized in the liver and kidney via proteolysis; no specific CYP450 enzymes involved.
Excretion	Renal: nearly 100% of absorbed dose, mostly as intact hormone; negligible biliary/fecal elimination.
Half-life	Terminal elimination half-life: 2-3 hours after subcutaneous administration; clinically, this necessitates daily or more frequent dosing.
Protein binding	Approximately 30-40%, primarily bound to growth hormone binding protein (GHBP) and low-affinity binding proteins.
Volume of Distribution	0.07-0.1 L/kg, indicating limited extravascular distribution; primarily confined to plasma volume.
Bioavailability	Subcutaneous: 75-85%; intramuscular: 80-90%; intravenous: 100%.
Onset of Action	Subcutaneous: 2-4 hours; intravenous: 15-30 minutes; intramuscular: 2-4 hours.
Duration of Action	Subcutaneous: 12-24 hours; intravenous: 8-12 hours; clinical effect duration shorter than metabolic clearance.

Classification & Brands

Action Class

Growth hormone agonist

Dosing & administration

Intramuscular or subcutaneous injection: 0.1-0.3 mg/kg/day (up to 0.6 mg/kg/day) divided into 1-2 doses. Typical adult dose for growth hormone deficiency: 0.2 mg/kg/day subcutaneously.

Dosage form	INJECTABLE
Renal impairment	No specific guidelines. Somatropin may be used in patients with renal impairment; however, monitoring for fluid retention and electrolyte imbalances is advised. GFR-based dose reduction is not established.
Liver impairment	No specific Child-Pugh based adjustments. Caution in severe hepatic impairment due to potential for decreased clearance; monitor for adverse effects.
Pediatric use	Growth hormone deficiency: 0.025-0.05 mg/kg/day subcutaneously once daily; maximum 0.1 mg/kg/day. For Turner syndrome: 0.05 mg/kg/day. For chronic renal insufficiency: 0.045-0.05 mg/kg/day.
Geriatric use	Use lowest effective dose. May require lower doses due to age-related changes in metabolism and increased risk of adverse effects such as fluid retention, arthralgia, and glucose intolerance. Regular monitoring of IGF-1 levels recommended.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for ZOMACTON (ZOMACTON).

Breastfeeding	Excretion into human milk is unknown; somatropin is a large protein and likely degraded in infant GI tract. No M/P ratio reported. Caution; benefit should outweigh risk.
Teratogenic Risk	No well-controlled studies in pregnant women. Animal studies are inadequate or inconclusive. Somatropin is not recommended during pregnancy unless clearly needed. First trimester: limited data suggests no increased malformation risk; second/third trimester: theoretical risk of maternal glucose intolerance and fetal growth acceleration.