SAIZEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SAIZEN (SAIZEN).
Recombinant human growth hormone (somatropin) binds to growth hormone receptors, activating JAK2/STAT5 signaling, leading to increased IGF-1 production, linear growth, and metabolic effects.
| Metabolism | Metabolized primarily in the liver and kidneys via proteolytic degradation; not metabolized by CYP450 enzymes. |
| Excretion | Primarily renal (glomerular filtration and tubular reabsorption). Approximately 70% of a dose is excreted unchanged in urine within 24 hours; minimal biliary or fecal elimination. |
| Half-life | Terminal elimination half-life is 2-3 hours after subcutaneous injection in adults; slightly longer in children (3-4 hours). The clinical relevance is that twice-daily dosing is often required for growth hormone replacement. |
| Protein binding | Approximately 40% bound, primarily to growth hormone-binding protein (GHBP) and, to a lesser extent, alpha-2-macroglobulin. |
| Volume of Distribution | 0.5-0.7 L/kg in adults, 0.3-0.6 L/kg in children. This moderate Vd indicates distribution primarily into extracellular fluid with limited tissue binding. |
| Bioavailability | Subcutaneous: 70-80% (average 75%) compared to intravenous administration. Intramuscular: ~60% (lower due to local degradation). |
| Onset of Action | Subcutaneous: Induction of IGF-1 levels begins within 2-4 hours; metabolic effects (e.g., lipolysis, protein synthesis) begin within 1-2 hours. Intravenous: Immediate, but not clinically used. |
| Duration of Action | Subcutaneous: Metabolic effects persist for 12-18 hours; IGF-1 levels remain elevated for up to 12 hours, supporting twice-daily dosing for growth promotion. |
| Action Class | Growth hormone agonist |
| Brand Substitutes | Norditropin Nordilet Injection |
Growth hormone deficiency: 0.005 mg/kg subcutaneously once daily; titrate based on response and IGF-1 levels. Typical adult maintenance dose: 0.2-0.5 mg/day subcutaneously.
| Dosage form | INJECTABLE |
| Renal impairment | Severe renal impairment (CrCl <30 mL/min): consider dose reduction by 50% or as guided by IGF-1 levels. |
| Liver impairment | No specific Child-Pugh based dosing guidelines; use with caution and monitor IGF-1 levels in hepatic impairment. |
| Pediatric use | Growth hormone deficiency: 0.025-0.035 mg/kg subcutaneously once daily; maximum 0.067 mg/kg/day. For growth failure in children: 0.05 mg/kg/day subcutaneously. |
| Geriatric use | Lowest effective dose recommended; start at 0.1-0.2 mg/day subcutaneously and titrate based on IGF-1 and clinical response, due to increased sensitivity and risk of adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SAIZEN (SAIZEN).
| Breastfeeding | Saizen is not recommended during breastfeeding. Exogenous somatropin may be excreted into human milk; the M/P ratio is unknown. Potential for adverse effects in the nursing infant, including growth promotion and metabolic effects. Decision to discontinue drug or breastfeeding should consider importance of drug to mother. |
| Teratogenic Risk | Saizen (somatropin) is not associated with an increased risk of major congenital malformations based on limited human data. For trimester 1, there is no evidence of teratogenicity. For trimester 2 and 3, continued use may be considered if maternal benefit outweighs risk, but growth hormone levels normally decline in pregnancy; exogenous growth hormone can cross the placenta and may affect fetal growth. No specific fetal adverse effects have been conclusively documented. |
■ 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. Risk of neoplasms: Monitor for new or recurrent malignancies in patients receiving growth hormone.
| Serious Effects |
["Active malignancy","Acute critical illness (e.g., open heart surgery, abdominal surgery, multiple trauma, acute respiratory failure)","Hypersensitivity to somatropin or excipients","Closed epiphyses in pediatric patients with growth failure","Children with PWS who are severely obese or have severe respiratory impairment","Active diabetic retinopathy"]
| Precautions | ["Increased risk of neoplasms (monitor for new or recurrent malignancies)","May cause fluid retention (e.g., peripheral edema, arthralgia, carpal tunnel syndrome)","Risk of slipped capital femoral epiphysis in children","Risk of pancreatitis","May induce glucose intolerance or diabetes mellitus","Intracranial hypertension (papilledema, headache, visual changes)","In PWS: risk of respiratory infection and sleep apnea; consider sleep study before initiation"] |
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| Fetal Monitoring | Monitor maternal blood glucose, hemoglobin A1c, thyroid function tests, and signs of fluid retention. For fetus, monitor growth via ultrasound due to possible effects on fetal growth velocity. Also monitor for gestational diabetes and hypertension. |
| Fertility Effects | Saizen may improve fertility in women with growth hormone deficiency by supporting folliculogenesis and endometrial receptivity. However, no direct adverse effects on fertility are reported. Use during pregnancy should be based on clinical need. |