Patient-Centric Drug Delivery: Establishing Injection Hold Time Limits for Large Volume Autoinjectors

Administering large volumes of medication via subcutaneous or intramuscular injection often requires tradeoffs to balance patient comfort with effective therapeutic outcomes. The shift toward patient-centric drug delivery has driven the development of large-volume autoinjectors (LVAI), enabling self-administration of medications outside clinical settings. However, little research has been conducted to establish an upper limit for autoinjector hold time. Therefore, this study seeks to establish an acceptable upper limit of hold time for most users by evaluating the capability of diverse user groups when performing simulated injection tasks. Using a mockup LVAI (>3mL), participants (N=20; Lay, Chronic Condition, Upper-Extremity impaired) completed two trials with two injections each: Trial A, hold as long as possible, and Trial B, hold for 10 minutes. Trials assessed maximum hold times and performance without progress cues. Grip strength, downward injection force, hold time, and subjective responses were recorded. When instructed, lay participants reliably maintained 10-minute injection time. Participants with chronic conditions and upper extremity impairments demonstrated significantly shorter and more variable hold times. Statistical analysis revealed no significant difference between pre- and postgrip strength, indicating effective fatigue management between trials. Every participant, regardless of group, was able to hold an injection for at least 2 minutes and 18 seconds. Subjective feedback indicated that most participants found 10-minute injections challenging, with a strong indications that durations of 2 minutes or less would be acceptable. Notably, participants were inaccurate in estimating injection duration, with perceived hold times deviating from actual by ~38%. For most users, an acceptable hold time for LVAIs is 2 minutes or less. Longer durations may be feasible but require additional design considerations, such as progress cues, end-of-dose feedback, and ergonomic support, to mitigate physical and mental challenges. Future research should expand to broader populations and balance risk-based factors that can further enhance the development of patient-centric drug delivery systems.