Background: The recent development of high-volume subcutaneous drug delivery using handheld autoinjectors has resulted in longer injection durations. However, the usability of long injections has been neglected. This study aimed to investigate the effects of injection duration on users' ability to apply injections while holding the device against the skin at the injection site. Methods: Thirty-two participants among patients, caregivers, and health-care professionals simulated three injections with different injection durations to evaluate usability and user's force. Linear and quantile regression were then applied to determine the impact of the injection duration on response variables related to user's force. Results: A significant negative effect of injection time was found on both the minimum and mean user's force applied. Initial empirical evidence was also determined on the negative association being more pronounced for users exerting lower force to hold the device against the skin. Conclusions:The results that are subject to future clinical validation suggest the feasibility of injections lasting up to approximately 30 s using handheld autoinjectors. The participants of the simulated use study successfully applied long-duration injections regardless of disease states, age, or visual and dexterity impairments. ARTICLE HISTORY

Purpose The subcutaneous delivery of biologics using pre-filled autoinjector devices continues to attract broad scholarly interests. However, research still lacks a detailed understanding of user perceptions as the basis for specifying the clinically relevant technical attributes of a device, such as the cap-removal force. Therefore, this article studies the ability of users to remove the autoinjector cap, as well as the effects of the cap-removal force and user characteristics on the perceived ease of decapping. Patients and Methods Forty-two participants among patients, caregivers, and healthcare professionals removed the protective cap using non-functional devices with different target cap-removal forces between 25 N and 55 N. Data were collected on the ability of the users to effectively decap the device and their perceived ease of decapping. Linear regression was then applied to quantify the impact of the decapping force and patient characteristics on the perceived ease of decapping. Results The participants of the study effectively decapped all autoinjector devices irrespective of age, sex, and dexterity impairments. Moreover, the study reveals that the perceived ease of decapping decreases significantly with increasing decapping force and participants’ dexterity impairments. Conclusion The study provides initial empirical evidence on the ability of users to decap autoinjector devices and shows how increasing the cap-removal force and dexterity impairments reduce the perceived ease of decapping.