ZORBTIVE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZORBTIVE (ZORBTIVE).
Recombinant human growth hormone that binds to growth hormone receptors, activating JAK2/STAT5 signaling pathway, leading to increased IGF-1 production and promotion of linear growth.
| Metabolism | Hepatic metabolism via proteolysis; primarily metabolized in the liver and kidneys. |
| Excretion | ZORBTIVE (somatropin) is eliminated primarily via the kidneys through glomerular filtration and tubular reabsorption. Approximately 70% of the dose is excreted renally as intact peptide, with 30% undergoing hepatic metabolism and biliary excretion. Fecal elimination accounts for less than 5%. |
| Half-life | Terminal elimination half-life of ZORBTIVE is approximately 2.5 hours after subcutaneous administration. For intravenous administration, the half-life is shorter at 0.6 hours. The longer subcutaneous half-life reflects sustained absorption from the injection site. |
| Protein binding | ZORBTIVE is approximately 30-40% bound to plasma proteins, primarily to growth hormone-binding protein (GHBP), which is a soluble fragment of the growth hormone receptor. A smaller fraction binds to albumin. |
| Volume of Distribution | Volume of distribution (Vd) for ZORBTIVE is 0.7-1.0 L/kg, indicating distribution into total body water and selective uptake by tissues with growth hormone receptors, such as liver, bone, and adipose tissue. |
| Bioavailability | Subcutaneous bioavailability of ZORBTIVE is approximately 70-80% due to presystemic degradation at the injection site. Intramuscular bioavailability is similar, 70-80%. Oral bioavailability is negligible (<1%) due to proteolytic degradation in the gastrointestinal tract. |
| Onset of Action | Subcutaneous: Onset of action is 2-4 hours for elevation of serum insulin-like growth factor 1 (IGF-1) levels. Intravenous: Immediate onset for metabolic effects (e.g., lipolysis, gluconeogenesis). Intramuscular: Onset similar to subcutaneous, 2-4 hours. |
| Duration of Action | Subcutaneous administration of ZORBTIVE yields a duration of action of 18-24 hours for growth-promoting effects, with daily dosing recommended. The metabolic half-life of IGF-1 induced by ZORBTIVE is approximately 15-20 hours. Clinical effects on linear growth require long-term administration (months to years). |
ZORBTIVE (somatropin) 0.006 mg/kg subcutaneously once daily for growth hormone deficiency in adults. Dose may be titrated based on clinical response and serum IGF-1 levels.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment guidelines are available for renal impairment. However, since somatropin is eliminated primarily via the kidneys, consider reducing dose in patients with severe renal impairment (GFR < 30 mL/min). Monitor response and IGF-1 levels closely. |
| Liver impairment | No specific dose adjustment guidelines for hepatic impairment. Use with caution in patients with severe hepatic disease; monitor clinical response and IGF-1 levels. |
| Pediatric use | For pediatric growth hormone deficiency: 0.025 to 0.05 mg/kg subcutaneously once daily. For pediatric patients with chronic kidney disease: 0.05 mg/kg per day. Dose adjustments based on growth response and IGF-1 levels. Dosing may vary by indication and patient age. |
| Geriatric use | In elderly patients, start at 0.003 mg/kg subcutaneously once daily, as older patients may have increased sensitivity to growth hormone. Titrate based on IGF-1 levels and clinical response, with a goal of maintaining serum IGF-1 levels within age- and gender-appropriate normal range. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZORBTIVE (ZORBTIVE).
| Breastfeeding | It is not known whether somatropin is excreted in human milk. Many endogenous hormones, including growth hormone, are excreted in breast milk. Due to the lack of specific data and potential for adverse effects in the nursing infant, caution is advised. The M/P ratio for exogenous somatropin has not been determined. Consider the developmental and health benefits of breastfeeding along with the mother's clinical need for ZORBTIVE and any potential adverse effects on the breastfed infant from the drug or underlying maternal condition. |
| Teratogenic Risk | ZORBTIVE (somatropin) is not indicated for use in pregnancy. However, based on its mechanism as recombinant human growth hormone, animal studies have shown no evidence of teratogenicity at doses up to 10 times the human dose. There are no adequate and well-controlled studies in pregnant women. Risk cannot be ruled out. During the first trimester, inadvertent exposure is not expected to increase malformation risk. Second and third trimester effects on fetal growth are unknown; potential for maternal hyperglycemia may affect fetal growth. |
■ FDA Black Box Warning
Increased mortality in patients with acute critical illness due to complications after open heart surgery, abdominal surgery, or multiple accidental trauma, or those with acute respiratory failure. ZORBTIVE is contraindicated in such patients.
| Serious Effects |
["Acute critical illness (e.g., open heart surgery, abdominal surgery, multiple trauma, acute respiratory failure)","Active malignancy","Hypersensitivity to somatropin or any excipients","Children with closed epiphyses (for pediatric growth indications)","Diabetic retinopathy (active proliferative or non-proliferative)"]
| Precautions | ["Increased risk of neoplasms (benign and malignant) in patients with pre-existing tumors or high risk","May cause fluid retention and edema","Risk of glucose intolerance and new-onset diabetes","Intracranial hypertension (pseudotumor cerebri) associated with rapid growth","Slipped capital femoral epiphysis in children","Progression of scoliosis in children","Hypersensitivity reactions including anaphylaxis","Pancreatitis risk","In children with CKD, monitor for hip displacement and renal osteodystrophy"] |
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| Fetal Monitoring | Monitor maternal blood glucose and thyroid function (TSH, free T4) throughout pregnancy as growth hormone may alter insulin sensitivity and thyroid hormone metabolism. Monitor fetal growth via ultrasound due to potential effects on maternal glucose control and growth hormone levels. Assess fetal well-being with appropriate prenatal testing if growth abnormalities are detected. No specific fetal monitoring is required beyond standard obstetric care unless complications arise. |
| Fertility Effects | Growth hormone deficiency may impair fertility; replacement therapy with somatropin may improve reproductive function. There is no evidence of specific adverse effects on fertility from ZORBTIVE. In animal studies, no impairment of fertility was observed. In humans, correction of growth hormone deficiency can restore ovulatory cycles in women and sperm production in men. |