somatropin (recombinant) (Omnitrope)

General

**BEERS Drug**

Pronunciation:
soe-ma-troe-pin


Trade Name(s)

  • Omnitrope

Ther. Class.

hormones

Pharm. Class.

growth hormones

Indications

  • Growth failure in children due to deficiency of growth hormone.
  • Children with growth failure associated with Prader-Willi syndrome or Turner syndrome.
  • Children with short stature born small for gestational age with no catch-up growth by age 2 yr.
  • Children with idiopathic short stature.
  • Growth hormone deficiency in adults as a result of pituitary disease, hypothalamic disease, surgery, radiation, trauma, or childhood onset.

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.
  • Growth hormone enhances GI tract mucosal transport of water, electrolytes, and nutrients.

Therapeutic Effect(s):

  • Increased skeletal growth in children with growth hormone deficiency.
  • Replacement of somatropin in deficient adults.

Pharmacokinetics

Absorption: Well absorbed.

Distribution: Localize to highly perfused organs (liver, kidneys).

Metabolism and Excretion: Broken down in renal cells to amino acids that are recirculated; some liver metabolism.

Half-life: 2.5–2.8 hr.

TIME/ACTION PROFILE (growth)

ROUTEONSETPEAKDURATION
SUBQwithin 3 mounknownunknown

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity to growth hormone or any of the excipients;
  • Closure of epiphyses;
  • Active malignancy;
  • Acute critical illness secondary to complications of open heart surgery, abdominal surgery or trauma, or those with acute respiratory failure;
  • Diabetic retinopathy;
  • Prader-Willi syndrome with severe obesity, upper airway obstruction, sleep apnea, or severe respiratory impairment (↑ risk of fatal complications);
  • OB:   Pregnancy.

Use Cautiously in:

  • Growth hormone deficiency due to intracranial lesion;
  • Pituitary hormone deficiency or hypoadrenalism;
  • Diabetes (may cause insulin resistance);
  • Scoliosis (may cause progression);
  • Turner syndrome with otitis media or cardiovascular disorders (may cause progression);
  • Thyroid dysfunction;
  • Lactation:  Safety not established in breastfeeding;
  • Pedi:  Contains benzyl alcohol (may cause fatal gasping syndrome in neonates);
  • Pedi:  Childhood cancer survivors (↑ risk of intracranial tumors);
  • Geri:  Appears on Beers list. ↑ risk of edema, arthralgia, carpal tunnel syndrome, gynecomastia, and impaired fasting glucose in older adults. Avoid use in older adults, except for confirmed growth hormone deficiency due to an established etiology.

Adverse Reactions/Side Effects

CV: peripheral edema

Endo: hypothyroidism, hyperglycemia, insulin resistance

GI: PANCREATITIS

Hemat: eosinophilia

Local: pain at injection site, local lipoatrophy or lipodystrophy

MS: arthralgia

Neuro: headache, intracranial hypertension

Misc: HYPERSENSITIVITY REACTIONS (including anaphylaxis and angioedema)

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

  • In patients requiring  glucocorticoid/corticosteroid  replacement or supplementation, careful titration is required as some metabolic pathways are inhibited by somatropin.
  • May alter clearance of compounds known to be metabolized by CYP450 liver enzymes, including  corticosteroids,  steroidal hormones,  anticonvulsants, and  cyclosporine.
  •  Estrogen  may ↑ requirements for somatropin.
  • May alter response to  insulin  and/or  oral hypoglycemic agents ; dose adjustment may be necessary.

Route/Dosage

Adult Growth Hormone Deficiency

SUBQ (Adults): 0.04 mg/kg/wk divided into equal doses given 7 days per wk initially; may ↑ at 4–8-wk intervals to a maximum of 0.08 mg/kg/wk.

Pediatric Growth Hormone Deficiency

SUBQ (Children): 0.16–0.24 mg/kg/wk divided into equal doses given 6–7 times per wk.

Growth Failure Associated with Prader-Willi or Turner Syndrome

SUBQ (Children): Prader-Willi syndrome:  0.24 mg/kg/wk divided into equal doses given 6–7 times per wk;  Turner syndrome:  0.33 mg/kg/wk divided into equal doses given 6–7 times per wk.

Short Stature Born Small for Gestational Age

SUBQ (Children): Up to 0.48 mg/kg/wk divided into equal doses given 6–7 times per wk.

Idiopathic Short Stature

SUBQ (Children): Up to 0.47 mg/kg/wk divided into equal doses given 6–7 times per wk.

Availability

Solution for injection (cartridges for use with pen device): 5 mg/1.5 mL, 10 mg/1.5 mL

Powder for injection: 5.8 mg/vial

Assessment

  • Growth Failure: Monitor bone age annually and growth rate determinations, height, and weight every 3–6 mo during therapy.

Lab Test Considerations:

Monitor thyroid function prior to and during therapy. May decrease T4 , radioactive iodine uptake, and thyroxine-binding capacity. Hypothyroidism necessitates concurrent thyroid replacement for growth hormone to be effective. Serum inorganic phosphorus, alkaline phosphatase, and parathyroid hormone may ↑ with somatropin therapy.

  • Monitor blood glucose periodically during therapy. Patients with diabetes may require ↑ insulin dose.
  • Monitor for development of neutralizing antibodies if growth rate does not exceed 2.5 cm/6 mo.
  • Monitor alkaline phosphatase closely in patients with adult growth hormone deficiency.

Implementation

  • Rotate injection sites with each injection.

    • After initial injection, use within 4 wk (3 wk for 5.8 mg vial) if stored in refrigerator.

Patient/Family Teaching

  • Instruct patient and parents on correct procedure for reconstituting medication, site selection, technique for SUBQ 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).
  • Assure parents and child that these dose forms are synthetic and therefore not capable of transmitting Creutzfeldt-Jakob disease, as was the original somatropin, which was extracted from human cadavers.
  • Advise parents to monitor blood glucose closely in children with diabetes mellitus. Parents should also be advised to report persistent severe abdominal pain (may be a symptom of pancreatitis) and signs and symptoms of hypersensitivity reactions (rash, facial swelling, difficulty breathing) immediately to health care professional.
  • Rep:  Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
  • Emphasize need for regular follow-up with endocrinologist to ensure appropriate growth rate, evaluate lab work, and 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.