somatropin (recombinant)

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 effects:

Increased skeletal growth in children with growth hormone deficiency.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed (70%).

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

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

Half-Life: 2.7 hr.

Time/Action Profile ⬆ ⬇

(growth)

ROUTE	ONSET	PEAK	DURATION
SUBQ	within 3 mo	unknown	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity to growth hormone or metacresol preservative or benzyl alcohol;
Closure of epiphyses;
Active neoplasia;
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 obesity and respiratory impairment (risk of fatal complications; can be used only if growth hormone deficiency is documented);
OB: Pregnancy.

Use Cautiously in:

Growth hormone deficiency due to intracranial lesion;
Pituitary hormone deficiency or hypoadrenalism;
Diabetes (may cause insulin resistance);
Thyroid dysfunction;
Lactation: Safety not established in breastfeeding;
Pedi: Neonates (diluent contains benzyl alcohol and may cause fatal gasping syndrome); 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.

Adv. Reactions/Side Effects ⬆ ⬇

CV: edema of the hands and feet

Endo: hyperglycemia, hypothyroidism, insulin resistance

GI: PANCREATITIS

Local: pain at injection site, local lipoatrophy or lipodystrophy

MS: arthralgia

Misc: HYPERSENSITIVITY REACTIONS (INCLUDING ANAPHYLAXIS AND ANGIOEDEMA)

Interactions ⬆ ⬇

Drug-drug:

Excessive corticosteroid use (equivalent to 10–15 mg/m²/day) may ↓ response to growth hormone.

Route/Dosage ⬆ ⬇

SC (Children ): Up to 0.1 mg/kg 3 times weekly.

Availability ⬆ ⬇

Lyophilized powder for injection: 5 mg/vial; 10 mg/vial

Assessment ⬆ ⬇

Growth Failure: Monitor bone age annually and growth rate determinations, height, and weight every 3–6 mo during therapy.
Assess and monitor for systemic hypersensitivity reactions (anaphylactic). Implement immediate medical treatment if needed.
Monitor for abdominal pain. May cause pancreatitis.

Lab Test Considerations:

Monitor thyroid function prior to and during therapy. May ↓ 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.
- ` Reconstitution: Reconstitute with 1–5 mL of bacteriostatic 0.9% NaCl for injection aiming the liquid against glass vial wall. Do not shake; swirl gently to dissolve. May be cloudy if refrigerated. Allow to warm to room temperature. If remains solution cloudy or contains particulate matter, do not use. Stable for 14 days when refrigerated; do not freeze.
SC: Injection volume should not exceed 1 mL. May be administered using a standard disposable syringe.

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy. Instruct patient and caregiver on correct procedure for reconstituting medication, site selection, technique for SUBQ injection, and disposal of needles and syringes. Review dose schedule. Persistent pain or edema at injection site should be reported to a health care professional.
Explain rationale for prohibiting 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; ↑ BP; hypertension).
Assure caregiver 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 caregiver to monitor blood glucose closely in children with diabetes mellitus. Caregivers 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.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

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