Aim
To summarize the similarities and differences among the somatropin products available in Canada.
Findings
The following somatropin products are presented in this section: Genotropin, Omnitrope, Humatrope, Nutropin, Saizen, and Norditropin. Serostim, another somatropin product available in Canada, has been omitted from this comparison because it is exclusively indicated for the treatment of HIV wasting associated with catabolism, weight loss, or cachexia. The information presented in the following tables was obtained from the current Canadian product monographs.13,22–28 It is important to note that the respective monographs have slight differences in the content, layout, and types of information. This is likely due to differences in product monograph requirements at the time of approval.
Manufacturing Information, Formulations, Indications, and Dosing
As illustrated in , all products use recombinant DNA technology in Escherichia coli host cells except Saizen, which is produced in mammalian source host cells. Biological activity was not reported for all products, but, when reported, it is 3 IU = 1 mg. Although not always reported, it is likely that all products contain some host cell impurities in the final formulation. The excipients used as preservatives or stabilizers vary greatly between formulations (lyophilized powder and solution) as well as among products. Some of the products contain benzyl alcohol, which is contraindicated in newborns. While all products except Norditropin are indicated for the treatment of growth hormone deficiency in both children and adults, several of the products have additional indications for the treatment of Turner syndrome, idiopathic short stature, children born small for gestational age, chronic renal insufficiency or failure, and short stature homeobox-containing gene deficiency.
Description of Somatropin Products.
All products, except Omnitrope and Norditropin, offer a lyophilized powder formulation that requires reconstitution before administration (see ). In addition, several products offer a stabilized solution either in a vial or in a pen with a cartridge ready for injection. All products are recommended for subcutaneous injection, and Nutropin, Humatrope, and Saizen can also be administered by intramuscular injection. The proprietary products are variable in their concentrations and administration formats. This is consistent with the variability in the recommended dosing for the different products, although the dosing recommendations for pediatric GHD and Turner syndrome appear to be more consistent among products than those for adult GHD. The inconsistency in formulations and in dosing recommendations adds to the complexity when a patient is switched from one product to another and could increase the potential for dosing errors.
Physical Description and Dosing of Somatropin Products.
Pharmacokinetics/Pharmacodynamics
Although there are slight differences in the pharmacokinetic profiles of the different somatropin products based on the available information (), these differences do not appear to be significant and are not expected to result in important clinical consequences. There is limited information on the pharmacodynamic properties of the other somatropin products in Canada. Omnitrope appears to have very similar pharmacodynamic properties to Genotropin ().
Pharmacokinetic Profile of Somatropin Products.
Pharmacodynamic Profile of Recombinant Human Growth Hormone Products.
Conclusion
The somatropin products indicated for the treatment of GHD have some differences in dosage forms and recommended dose, but have similar pharmacokinetic and pharmacodynamic profiles.