SOMATROPIN

(soe-ma-troe'pin)

Genotropin, Miniquick, Humatrope, Norditropin, Nutropin, Nutropin AQ, Omnitrope, Serostim, Serostim LQ, Saizen, Zorbtive
Classifications: hormone; growth hormone;
Therapeutic: growth hormone
Pregnancy Category: B, C (brand dependent)

Availability

1.5 mg, 4 mg, 5 mg, 5.8 mg, 6 mg, 8 mg, 10 mg injection

5 mg/1.5 mL, 15 mg/1.5 mL prefilled syringe

Action

New recombinant growth hormone with the natural sequence of 191 amino acids characteristic of endogenous growth hormone (GH).

Therapeutic Effect

Induces growth responses similar to those produced in children treated with GH obtained from human pituitary glands.

Uses

Growth failure due to GH deficiency; replacement therapy prior to epiphyseal closure in patients with idiopathic GH deficiency; GH deficiency secondary to intracranial tumors or panhypopituitarism; inadequate GH secretion; short stature in girls with Turner's syndrome; AIDS wasting syndrome; short bowel syndrome.

Contraindications

Patient with closed epiphyses; underlying progressive intracranial tumor, cresol hypersensitivity, glycerin hypersensitivity; diabetic retinopathy; respiratory insufficiency; during chemotherapy, radiation therapy, active neoplastic disease; Prader-Willi syndrome; untreated hypothyroidism, obesity; pregnancy (category B or category C depending on the brand).

Cautious Use

Diabetes mellitus or family history of the disease; history of upper airway obstruction, sleep apnea, or unidentified URI; lactation; concomitant or prior use of thyroid or androgens in prepubertal male; hypothyroidism; surgery, trauma; neonates with benzyl alcohol hypersensitivity; neonates; lactation.

Route & Dosage

Note: Dosing will vary with specific products

Growth Hormone Deficiency
Adult: SC Humatrope 0.006 mg/kg (0.018 IU/kg) q.d., may increase [max: 0.0125 mg/kg/d (0.0375 IU/kg/d)]; Nutropin, Nutropin AQ 0.006 mg/kg q.d. (max: <35 y, 0.025 mg/kg/d; >35 y, 0.0125 mg/kg/d)
Child: SC Genotropin 0.16–0.24 mg/kg/wk divided into 6–7 q.d. doses; Humatrope 0.18 mg/kg/wk (0.54 IU/kg/wk) divided into equal doses given on either 3 alternate days or 6 times/wk; Norditropin 0.024–0.034 mg/kg/d 6–7 times/wk; Nutropin, Nutropin AQ 0.3 mg/kg/wk (0.9 IU/kg/wk) divided into 6–7 q.d. doses

Inadequate Growth Hormone Secretion
Child: SC Nutropin 0.3 mg/kg every week

AIDS Wasting or Cachexia
Adult: SC Serostim >55 kg, 6 mg qh.s.; 45–55 kg, 5 mg qh.s.; 35–45 kg, 4 mg qh.s.; <35 kg, 0.1 mg/kg qh.s.

Short Bowel Syndrome
Adult: SC Zorbtive 0.1 mg/kg once daily for 4 wk (max: 8 mg/d)

Administration

Subcutaneous

Reconstitute each brand following its manufacturer's instructions (vary from brand to brand).
Read and carefully follow directions for use supplied with the Nutropin AQ Pen^TM Cartridge if this is the product being used.
Rotate injection sites; abdomen and thighs are preferred sites. Do not use buttocks until the child has been walking for a year or more and the muscle is adequately developed.
Store lyophilized powder at 2°–8° C (36°–46° F). After reconstitution, most preparations are stable for at least 14 d under refrigeration. DO NOT FREEZE.

Adverse Effects (≥1%)

Body as a Whole: Pain, swelling at injection site; myalgia. Fatalities reported in patients with Prader-Willi syndrome and one or more of severe obesity, history of respiratory impairment or sleep apnea, or unidentified respiratory infection, especially male patients. Metabolic: Hypercalciuria; over saturation of bile with cholesterol, hyperglycemia, ketosis. Endocrine: High circulating GH antibodies with resulting treatment failure, accelerated growth of intracranial tumor.

Interactions

Drug: anabolic steroids, thyroid hormone, androgens, estrogens may accelerate epiphyseal closure; ACTH, corticosteroids may inhibit growth response to somatropin.

Pharmacokinetics

Metabolism: In liver. Elimination: In urine. Half-Life: 15–50 min.

Nursing Implications

Assessment & Drug Effects

Assess bone age annually in all patients and especially those also receiving concurrent thyroid or androgen treatment, since these drugs may precipitate early epiphyseal closure. Urge parent to take child for bone age assessment on appointed annual dates.
Lab test: Periodic serum and urine calcium and plasma glucose.
Hypercalciuria, a frequent adverse effect in the first 2–3 mo of therapy, may be symptomless; however, it may be accompanied by renal calculi, with these reportable symptoms: flank pain and colic, GI symptoms, urinary frequency, chills, fever, hematuria.
Test for circulating GH antibodies (antisomatropin antibodies) in patients who respond initially but later fail to respond to therapy.
Observe diabetics or those with family history of diabetes closely. Obtain regular urine for glycosuria or fasting blood glucose and HbA_1C.
Examine patients with GH deficiency secondary to intracranial lesion frequently for progression or recurrence of underlying disease.

Patient & Family Education

Be aware that during first 6 mo of successful treatment, linear growth rates may be increased 8–16 cm or more per year (average about 7 cm/y or approximately 3 in.). Additionally, SC fat diminishes but returns to pretreatment value later.
Record accurate height measurements at regular intervals and report to physician if rate is less than expected.
In general, growth response to somatropin is inversely proportional to duration of treatment.
Discontinue treatment when patient has reached satisfactory adult height, when epiphyses have fused, or when patient fails to exhibit growth response.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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