OBJECTIVES: Treatment of growth hormone deficiency involves daily subcutaneous injections of recombinant human growth hormone (rhGH) and takes place over many years, incurring substantial costs. Current administration devices exhibit rhGH wastage during everyday use. We therefore sought to assess the extent of product wastage with four rhGH administration devices. METHODS: Norditropin® FlexPro®, NordiFlex® and NovoPen®/SimpleXx® 5mg pens (Novo Nordisk A/S, Bagsværd, Denmark) and durable Omnitrope®Pen-5 devices (Sandoz, Holzkirchen, Germany) were tested (n=40 for each device type in each test). Total rhGH content and product wastage (rhGH lost before and after injection) were measured in GxP-compliant laboratory simulations of: time with the needle attached prior to injection, dose setting, and correcting a set dose. The mass of wasted rhGH from each pen was measured using an analytical balance and averaged over all devices. Statistical significance (p<0.05) was confirmed using a Student’s t-test and a mathematical model was constructed to estimate annual wastage. RESULTS: The mean rhGH mass wasted with the needle on prior to injection was 0.0µg with all Norditropin® pens, relative to 94µg with Omnitrope® devices. During dose dialing, 0.2–2.3µg of rhGH was lost with Norditropin® pens versus 0.8µg with Omnitrope® and during dose correction, 0.1–0.8µg of rhGH was wasted with Norditropin® pens versus 1.4µg with Omnitrope®. Mean total rhGH content was 5.09–5.19mg with Norditropin® compared to 5.06mg with Omnitrope®. All results were statistically significant. Annual wastage with Omnitrope® was projected to be 42.4mg per patient, compared to 5.5–8.3mg with Norditropin®. CONCLUSIONS: Overall, Norditropin® pens resulted in significantly less wastage when compared with Omnitrope®. Norditropin® pens were also found to contain significantly more rhGH than Omnitrope® devices. The study suggests that, in rhGH administration devices of the same nominal volume, differences exist that materially affect the frequency with which patients must refill their rhGH prescriptions.