In Vivo Somatropin Bioidentity Assay – USP <126>
Somatropin is a recombinant form of Somatotropin (growth hormone) and the somatropin in vivo bioassay to test for bioidentity follows the procedure described in USP <126>, Somatropin Bioidentity Tests. Somatropin is often used to treat growth failure, growth hormone deficiency, intestinal disorders, or HIV-related weight loss.
The somatropin test method exposes hypophysectomized rats to the drug product being tested, the USP somatropin reference standard and a negative control. The rats are weighed before the first injection and at approximately the 18th hour after the last subcutaneous injection. The change in body weight for each animal in each group is recorded and the potency of the drug product relative to the potency of the USP reference standard is computed. The acceptance criteria for the assay is a potency value of the drug product of 2 USP Somatropin Units/mg or higher with confidence limits of 63%-158% of the calculated potency.