somatropin rDNA

somatropin rDNA (injection)

(soe-ma-troe-pin),

Valtropin

(trade name)

Classification

Therapeutic: hormones
Pharmacologic: growth hormones
Pregnancy Category: B

Indications

Growth failure in children with inadequate secretion of growth hormone including patients with Turner syndrome who have open epiphyses.Replacement of endogenous growth hormone in adults with deficiency (alone or associated with pituitary pathology, hypothalamic disease, surgery, radiation or trauma) or history of deficience as a child.

Action

Produce growth (skeletal and cellular). Metabolic actions include: Increased protein synthesis, Increased carbohydrate metabolism, Lipid mobilization, Retention of sodium, phosphorus, and potassium. Somatropin has the same amino acid sequence as naturally occurring growth hormone and is produced by recombinant DNA techniques in yeast cells. Growth hormone enhances GI tract mucosal transport of water, electrolytes and nutrients.

Therapeutic effects

Increased skeletal growth in children with growth hormone deficiency. Replacement of somatropin in deficient adults. Increased bone density in adult growth hormone–deficient patients.

Pharmacokinetics

Absorption:
Distribution:
Metabolism and Excretion:
Half-life: 3.03 hr

Time/action profile (blood levels)

ROUTEONSETPEAKDURATION
SCunknown4 hr 24 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity to metacresol in diluent (other diluent should be substituted)Promotion of growth in children with closed epiphyses;Active proliferative/severe non-proliferative diabetic retinopathy;Acute critical illness including complications of open-heart/abdominal surgery, multiple trauma or respiratory failure; Active or progressive malignancy;Prader-Willi syndrome with severe obesity/respiratory impairment without documented growth hormone deficiency (↑ risk of mortality, especially in males).
Use Cautiously in: Cranial lesions (observe frequently for progression); Diabetes mellitus (↓ insulin sensitivity);Undiagnosed central hypoadrenalism (may become unmasked during treatment;Hypopituitarism (replacement of additional hormones is necessary);Hypothyroidism (may ↓ response);Turner syndrome (monitor for otitis media/hearing loss, skeletal and cardiovascular abnormalities; Geriatric: Elderly patients may be ↑ sensitive to drug effects and have ↑ risk of adverse reactions (lowers doses/smaller increments recommended); Obese patients (may experience ↑ risk of adverse reactions when given a weight-based dose);Estrogen-replete women ( may require ↑ dose); Lactation: Use cautiously in breastfeeding women; Obstetric: Use during only if clearly needed.

Adverse Reactions/Side Effects

Central nervous system

  • intracranial hypertension

Cardiovascular

  • edema of hands and feet (↑ in adults)

Endocrinologic

  • hyperglycemia
  • ↓ insulin insensitivity
  • rapid growth

Interactions

Drug-Drug interaction

Excessive corticosteroid use (equivalent to 10–15 mg/m2/day) may ↓ response to growth hormone.May induce CYP450 enzymes and may ↓ effectiveness of drugs metabolized by CYP450.Oral estrogen may ↑ dose requirements.

Route/Dosage

Subcutaneous (Adults) 0.33 mg/day six days/week (0.005 mg/kg/day), may be carefully increased to 0.66 mg/day (0.01 mg/kg/day) six days/week; alternative dosing—0.2 mg/day, may be increased every 1–2 mos in increments of 0.1–0.2 mg/day. Lower doses and increments are recommended for elderly patients.
Subcutaneous (Children) Pediatric growth hormone deficiency (GHD)—0.17–0.3 mg/kg/week given in equally divided doses daily or for six out seven days/week; Turner syndrome—0.37 mg/kg/week given in equally divided doses daily or for six out seven days/week.

Availability

Powder for subcutaneous injection (requires reconstitution; diluent contains metacresol: 5 mg/vial packaged with single dose syringe containing 1.5 mL diluent (0.3% metacresol in water for injection)

Nursing implications

Nursing assessment

  • Monitor bone age annually and growth rate determinations, height, and weight every 3–6 mo during therapy.
  • Assess patients with Turner syndrome for otitis media and other ear disorders; may have increased risk of ear and hearing disorders.
  • Monitor for any malignant transformation of skin lesions.
  • Lab Test Considerations: May cause ↑ serum levels of inorganic phosphorus, alkaline phosphatase, parathyroid hormone (PTH) and IGF-I during somatropin therapy.
    • Monitor blood glucose periodically during therapy. Diabetic patients may require ↑ insulin dose.

Potential Nursing Diagnoses

Disturbed body image (Indications)

Implementation

  • Subcutaneous: Reconstitute with 1.5 mL of diluent provided or Sterile Water for Injection. Dilute by aiming the liquid against glass vial wall. Do not shake; swirl gently to dissolve. Solution is clear; do not use solutions that are cloudy or contain a precipitate. Discard unused solution diluted with water. Solutions diluted with diluent stable for 21 days; do not freeze. Thighs are preferred injection site. Rotate injection sites with each dose.

Patient/Family Teaching

  • Instruct patient and parents on correct procedure for reconstituting medication, site selection, technique for subcut injection, and disposal of needles and syringes. Review dose schedule. Parents should report persistent pain or edema at injection site.
  • Explain rationale for prohibition of use for increasing athletic performance. Administration to persons without growth hormone deficiency or after epiphyseal closure may result in acromegaly (coarsening of facial features; enlarged hands, feet, and internal organs; increased blood glucose; hypertension).
  • Advise parents to monitor blood glucose closely in children with diabetes mellitus.
  • Emphasize need for regular follow-up with endocrinologist to ensure appropriate growth rate, to evaluate lab work, and to determine bone age by x-ray exam.

Evaluation/Desired Outcomes

  • Child’s attainment of adult height in growth failure secondary to pituitary growth hormone deficiency. Therapy is limited to period before closure of epiphyseal plates (approximately up to 14–15 yr in girls, 15–16 yr in boys).
  • Replacement of growth hormone in deficient adults.