GENOTROPIN PRESERVATIVE FREE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GENOTROPIN PRESERVATIVE FREE (GENOTROPIN PRESERVATIVE FREE).
Somatropin, a recombinant human growth hormone (GH), binds to growth hormone receptors (GHR) on target cells, activating JAK2/STAT5 signaling, which stimulates hepatic IGF-1 synthesis, promotes linear skeletal growth, increases lean muscle mass, reduces adipose tissue, and affects carbohydrate, protein, and lipid metabolism.
| Metabolism | Metabolized in the kidneys and liver via proteolytic degradation; not a substrate for CYP450 enzymes. |
| Excretion | Primarily renal: about 70% of the dose is excreted via glomerular filtration and tubular reabsorption. A small portion (approximately 20%) is eliminated via biliary/fecal routes as metabolites. |
| Half-life | Terminal elimination half-life: approximately 2-3 hours following subcutaneous administration in adults. In children, half-life may be slightly longer (2-3.5 hours). Clinical context: supports once-daily or multiple daily dosing regimens. |
| Protein binding | Approximately 30-50% bound to growth hormone binding protein (GHBP) and other plasma proteins. |
| Volume of Distribution | Vd: approximately 0.07-0.1 L/kg in adults, indicating limited distribution beyond intravascular space. Higher in children (0.1-0.2 L/kg). Clinical meaning: reflects primarily plasma and extracellular fluid distribution. |
| Bioavailability | Subcutaneous: approximately 80% (range 75-87%). Intramuscular: similar to subcutaneous. Intravenous: 100% (but not the intended route). |
| Onset of Action | Subcutaneous: clinical effects (elevation of IGF-1 levels) observed within 3-6 hours after a single dose; metabolic effects (e.g., lipolysis) detectable within 1-2 hours. |
| Duration of Action | Duration of metabolic effects (e.g., increased protein synthesis, lipolysis) persists for 12-24 hours. Clinical notes: once-daily dosing achieves sustained effects; growth promotion requires chronic therapy over months to years. |
0.2-0.6 mg subcutaneously daily
| Dosage form | INJECTABLE |
| Renal impairment | CrCl <50 mL/min: reduce dose by 50%; CrCl <20 mL/min: avoid use |
| Liver impairment | Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated |
| Pediatric use | 0.025-0.05 mg/kg/day subcutaneously (max 0.1 mg/kg/day) |
| Geriatric use | Use lower end of adult dosing range, monitor for fluid retention and glucose intolerance |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GENOTROPIN PRESERVATIVE FREE (GENOTROPIN PRESERVATIVE FREE).
| Breastfeeding | Somatropin is not detectable in breast milk. M/P ratio unknown. Considered compatible with breastfeeding. |
| Teratogenic Risk | Limited data; no evidence of teratogenicity in animal studies. Insufficient human data for first trimester. No known fetal risk in second and third trimesters, but use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
Increased mortality in patients with acute critical illness due to complications following open heart surgery, abdominal surgery, multiple accidental trauma, or acute respiratory failure. Not approved for these uses.
| Serious Effects |
["Acute critical illness (e.g., open heart, abdominal, multiple trauma surgeries, acute respiratory failure)","Active malignancy","Children with Prader-Willi syndrome who are severely obese or have severe respiratory impairment","Hypersensitivity to somatropin or any excipients","Closed epiphyses in pediatric patients for treatment of growth failure","Active diabetic retinopathy"]
| Precautions | Increased risk of neoplasms, benign intracranial hypertension (pseudotumor cerebri), slipped capital femoral epiphysis, pancreatitis, insulin resistance/diabetes, exacerbation of preexisting scoliosis, fluid retention, secondary hypothyroidism, and withdrawal of therapy may unmask hypothyroidism. Monitor for glucose intolerance, thyroid status, and signs of increased intracranial pressure. |
| Food/Dietary | No significant food interactions. However, growth hormone can affect glucose metabolism; monitor blood glucose in diabetic patients. Avoid high-carbohydrate meals around the time of injection if glucose control is an issue. |
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| Monitor maternal glucose tolerance and thyroid function. Assess fetal growth via ultrasound if used in pregnancy. |
| Fertility Effects | Somatropin may improve fertility in women with growth hormone deficiency or poor ovarian response. No adverse effects on fertility reported. |
| Clinical Pearls | For optimal accuracy, reconstitute with bacteriostatic water for injection (0.9% benzyl alcohol) not sterile water. Use a low-dead-volume syringe to minimize drug loss. Avoid vigorous shaking; swirl gently. Rotate injection sites to prevent lipohypertrophy. Monitor serum IGF-1 levels 4-6 weeks after starting or adjusting dose. In children, obtain annual bone age X-rays. Discontinue if closure of epiphyseal plates occurs. |
| Patient Advice | Store the vial in the refrigerator between 36°F to 46°F (2°C to 8°C). Do not freeze. · After reconstitution, use within 14 days if refrigerated. · Inject subcutaneously, not into a vein or muscle. · Rotate injection sites to avoid lumps or skin damage. · Do not share your pen or needles with others. · Report any signs of increased intracranial pressure (severe headache, vision changes, nausea/vomiting). |