Feasibility of switching between different autoinjector designs: positive insights from formative Comparative Use Human Factors studies

Users may switch drug-device products when transitioning to generic versions. For autoinjectors, such switches can involve user interface differences, particularly in the activation mechanism, requiring either a push-on-skin step or button activation. It is essential to demonstrate that the use of a generic product remains safe and effective. This article provides preliminary usability data on various autoinjector designs, focusing on generic drug-device combination products. Two formative Comparative Use Human Factors studies assessed the usability of a 3-step candidate generic button-activated autoinjector compared to RLD autoinjectors: study 1 compared it to a 4-step button-activated while study 2 compared it to a 2-step push-on-skin. In study 1, 80% of participants (12/15) performed similarly with both devices. The error rate for the 3-step candidate generic autoinjector was 20% (3/15), compared to 13.3% (2/15) for the 4-step. In study 2, 90% of participants (10/11) performed similarly with both devices, with a 9% (1/11) error rate for the 3-step candidate generic autoinjector and 0% for the 2-step. These studies offer preliminary evidence supporting the feasibility of switching between different autoinjector activation mechanisms without introducing new risks. The main driver of usability results appears to be user familiarity rather than design differences.