Biological potency is determined using a cell proliferation bioassay. Phosphoric acid may be used for pH adjustment. Bacteriostatic Water for Injection, USP, is a sterile water containing 0.9 percent benzyl alcohol per mL as an antimicrobial preservative packaged in a multi-dose vial. In vitro and in vivo preclinical and clinical testing have demonstrated that Protropin is therapeutically equivalent to pituitary-derived human growth hormone. Protropin stimulates skeletal growth in children with growth failure due to a lack of adequate secretion of endogenous growth hormone.
Skeletal growth is accomplished at the epiphyseal plates at the ends of a growing bone.
New bone is formed at the epiphyses in response to growth hormone. This results in linear growth until these growth plates fuse at the end of puberty. Growth hormone of human pituitary origin influences the size of internal organs, including kidneys, and increases red cell mass. Treatment of hypophysectomized or genetic dwarf rats with somatropin results in organ growth that is proportional to the overall body growth. This is reflected by nitrogen retention as demonstrated by a decline in urinary nitrogen excretion and blood urea nitrogen during growth hormone therapy.