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As with all protein pharmaceuticals, a small percentage of patients may develop antibodies to the protein. Growth hormone antibody binding capacities below 2 mg/L have not been associated with growth attenuation. In some cases when binding capacity exceeds 2 mg/L, growth attenuation has been observed. In clinical studies and postmarketing experience of patients treated with Protropin® (somatrem for injection), approximately 0.4 percent of patients screened for antibody production developed antibodies with binding capacities > 2 mg/L at six months. Out of approximately 26,000 patients who have been treated with Protropin (somatrem) , 5 patients have had growth deceleration associated with binding capacities > 2 mg/L. If growth deceleration is observed that is not attributable to another cause, the patient should be tested for antibodies to growth hormone. Although no evidence exists to indicate that the methionine on the N-terminus of somatrem causes antibodies to growth hormone, the physician should consider transferring the patient to somatropin (rDNA origin) for injection, if a patient has antibody binding capacity > 2 mg/L, and has exhibited growth attenuation.
In addition to an evaluation of compliance with the prescribed treatment program and thyroid status, testing for antibodies to human growth hormone should be carried out in any patient who fails to respond to therapy.
Additional short-term immunologic and renal function studies were carried out in a group of patients after approximately two years of treatment to detect other potential adverse effects of antibodies to growth hormone. The antibody was determined to be of the IgG class; no antibodies to growth hormone of the IgE class were detected. Testing included immune complex determination, measurement of total hemolytic complement and specific complement components, and immunochemical analyses. No adverse effects of growth hormone antibody formation were observed.
These findings are supported by a toxicity study conducted in a primate model in which a similar antibody response to growth hormone was observed. Protropin (somatrem) , administered to monkeys by intramuscular injection at doses of 125 and 625 ug/kg TIW, was compared to pituitary-human growth hormone at the same doses and with placebo over a period of 90 days. Most monkeys treated with high-dose Protropin (somatrem) developed persistent antibodies at week four. There were no biologically significant drug related changes in standard laboratory variables. Histopathologic examination of the kidney and other selected organs (pituitary, lungs, liver and pancreas) showed no treatment related toxicity. There was no evidence of immune complexes or immune complex toxicity when the kidney was also examined for the presence of immune complexes and possible toxic effects of immune complexes by immunohistochemistry and electron microscopy.
In studies in children treated with Protropin (somatrem) , injection site pain was reported infrequently.
Leukemia has been reported in a small number of growth hormone deficient patients treated with growth hormone. It is uncertain whether this increased risk is related to the pathology of growth hormone deficiency itself, growth hormone therapy, or other associated treatments such as radiation therapy for intracranial tumors. On the basis of current evidence, experts cannot conclude that growth hormone therapy is responsible for these occurrences. The risk to an individual patient, if any, remains to be established.
Other adverse drug reactions that have been reported in growth hormone-treated patients include the following: 1) Metabolic: Infrequent, mild and transient peripheral edema. 2) Musculoskeletal: Rare carpal tunnel syndrome. 3) Skin: Rare increased growth of pre-existing nevi. Malignant nevi transformation has not been reported. 4) Endocrine: Rare gynecomastia. Rare pancreatitis.
Read the Protropin (somatrem) Side Effects Center for a complete guide to possible side effects
Concomitant glucocorticoid therapy may inhibit the growth promoting effect of Protropin (somatrem) . If glucocorticoid replacement is required, the dose should be carefully adjusted.
Last reviewed on RxList: 12/8/2004
This monograph has been modified to include the generic and brand name in many instances.
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