Background: A reduced injection force potentially makes it easier for patients to administer their injected medication.
Objective and Hypotheses: This report compares dose force, dose accuracy and dose precision of two growth hormone injection devices: Norditropin® NordiFlex® (NF) (Novo Nordisk A/S, Denmark) and Genotropin® GoQuick® (GQ) (Pfizer Inc, NY, USA).
Methods: Mean of maximum dose force was determined for a 1.5 mg dose at speeds of 4, 6 and 8 mm/s for NF and GQ pens and was measured in 25 pens of each type. Dose accuracy and precision were assessed at 0.1, 0.75 and 1.5 mg doses (60 measurements at each level) in 30 pens of each type. Both pens were fitted with a NovoFine 32 G x 6 mm needle. Testing was done at 20°C, 45% relative humidity. Dose force was measured with a tensile testing machine in compression mode (Lloyd, LRx plus) (ID: 24K-04-115) and transducer (measuring cell) of max 100 N (ID: 24K-04-082). Dose accuracy and precision were assessed using an analytical balance (ID: MS7813) and METDose data system (ID: LP38188).
Results: Estimated relative dose force (N/N) for NF was significantly lower than for GQ (1.4, 1.5, 1.5; P<0.0001) at all speeds (4, 6, 8 mm/s). Dose accuracy at 0.10, 0.75 and 1.50 mg doses was 101, 99 and 99% for NF and 100, 95 and 97% for GQ, respectively. Dose precision (CV, %) was 3.8, 0.7 and 0.7 for NF and 11.1, 2.6 and 1.6 for GQ.
Conclusions: Dose force was significantly lower for NF than for GQ. Dose accuracy was not dissimilar between devices but dosing precision was improved with NF vs. GQ.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.