OBJECTIVES: To assess the cost of various market share scenarios of leading recombinant human growth hormone (rhGH) pens to a commercial health plan, taking into consideration drug and wastage costs due to device design. METHODS: A budget impact model (BIM) was developed to determine the costs of rhGH products. Key model inputs included plan size, number of pediatric and adult patients, mean [SD] weight, product dosing increments and annual wastage due to pen devices having varying dosing increments. The BIM included storage and reconstitution wastage as an option. Pediatric (n=900) and adult (n=100) patient weights were assumed to be normally distributed with mean (SD) 30.25 (4.00) and 75.00 (2.00) kg. Assumed base case dosages were 0.03 mg/kg daily for pediatric patients; brand-specific based on product package inserts for adult patients. Market share was indexed at Year 1 (2011) and presented with 10%, 15% and 20% shifts to Norditropin from Genotropin, Humatrope, and Nutropin. Costs were based on WAC in US dollars. RESULTS: Costs per patient per year (PPPY) were higher for Genotropin, Humatrope and Nutropin vs. Norditropin ranging from approximately $23.1K to $24.6K in pediatrics and $8.1 K to $9.2K in adults. Norditropin was associated with the lowest annual milligrams of wastage (9.1 mg pediatric/ 8.5 mg adult, including wastage due to storage and reconstitution) across all pen dosages, followed by Nutropin (20.7 mg/ 19.9 mg), Humatrope (20.7 mg/20.2 mg) and Genotropin (30.6 mg/ 30.3 mg). Norditropin remained the least costly per year when: dosing from package inserts was used, adult dosing was fixed, and when storage and reconstitution wastage was not included. CONCLUSIONS: Due to differences in cost per mg and wastage associated with design among the leading GH brands on the market, use of Norditropin pens may result in cost savings.