What is the appropriate dose of somatropin (growth hormone) for a patient weighing 66 pounds?

Somatropin Dosing for a 66-Pound Patient

For a pediatric patient weighing 66 pounds (30 kg) with growth hormone deficiency, the appropriate dose of somatropin is 4.8-7.2 mg per week, divided into 6-7 daily subcutaneous injections (approximately 0.7-1.0 mg per day). 1

Dose Calculation Based on Indication

The specific weekly dose depends on the underlying diagnosis:

Pediatric Growth Hormone Deficiency (GHD)

• Weekly dose: 4.8-7.2 mg (0.16-0.24 mg/kg/week for a 30 kg patient) 1
• Divide into 6-7 daily subcutaneous injections
• This translates to approximately 0.7-1.0 mg per day 1

Prader-Willi Syndrome (PWS)

• Weekly dose: 7.2 mg (0.24 mg/kg/week for a 30 kg patient) 1
• Critical contraindication: Do not use if the patient is severely obese, has upper airway obstruction, sleep apnea, or severe respiratory impairment, as sudden death has been reported 1

Turner Syndrome (TS)

• Weekly dose: 9.9 mg (0.33 mg/kg/week for a 30 kg patient) 1
• Divide into 6-7 daily injections

Small for Gestational Age (SGA)

• Weekly dose: up to 14.4 mg (up to 0.48 mg/kg/week for a 30 kg patient) 1
• This represents the highest approved pediatric dose

Idiopathic Short Stature (ISS)

• Weekly dose: up to 14.1 mg (up to 0.47 mg/kg/week for a 30 kg patient) 1

Administration Guidelines

Injection Technique

• Administer via subcutaneous injection daily, preferably in the evening 1
• Rotate injection sites between thigh, buttocks, and abdomen to avoid lipoatrophy 1
• The weekly dose must be divided over 6 or 7 days—never give the entire weekly dose at once 1

Monitoring Requirements

• First-year growth response is critical: Failure to increase growth rate during the first year indicates need for compliance assessment and evaluation for other causes of growth failure (hypothyroidism, undernutrition, advanced bone age, or antibodies to recombinant human GH) 1
• Response to somatropin tends to decrease with time, requiring ongoing monitoring 1
• Adherence to daily injections is essential—children with high adherence to daily somatropin injections grow significantly more than those with low adherence 2

Treatment Duration

• Discontinue treatment when epiphyses are fused, as further growth is not possible 1

Critical Safety Considerations

Absolute Contraindications

• Acute critical illness (post-cardiac surgery, abdominal surgery, multiple trauma, or acute respiratory failure) 1
• Prader-Willi Syndrome patients who are severely obese with upper airway obstruction, sleep apnea, or severe respiratory impairment 1

Dosing Adjustments

• Obese patients may require dose adjustment: The FDA label notes that obese individuals are more likely to manifest adverse effects when treated with weight-based regimens, though specific pediatric obesity adjustments are not detailed 1
• Dosage must be individualized based on growth response, not arbitrarily increased 1

Common Pitfalls to Avoid

• Do not give weekly dose as single injection: The dose must be divided over 6-7 days to maintain therapeutic levels and minimize adverse effects 1
• Do not continue treatment without monitoring growth velocity: Lack of growth response in the first year requires immediate reassessment 1
• Do not overlook injection site rotation: Failure to rotate sites leads to lipoatrophy 1
• Do not shake reconstituted vials: Shaking may denature the active ingredient—swirl gently instead 1

Expected Outcomes

• Somatropin produces protein anabolic effects and increases lean body mass when used appropriately 3
• The medication is safe and effective with low immunogenicity when administered as prescribed 4
• Approximately 3 patients per 21 may develop serum antibodies to GH, but clinically significant antibody formation (>1.0 mg/L binding capacity) is rare and typically does not attenuate growth response 4