Improving prefilled syringe injectability: influences of critical component attributes and human factors.

Prefilled syringes (PFSs) have emerged as a predominant primary packaging format for subcutaneous biopharmaceutical drug products. Subcutaneous administration typically requires low injection volumes and high drug concentrations, which frequently leads to a nonlinear increase in viscosity; that can impair injectability and feasibility for patient self-administration, potentially affecting drug safety and efficacy. This research investigates critical PFS design elements (including silicone oil coating, barrel diameter, plunger stopper contact length, needle length and inner diameter) that can be optimized to further mitigate injection resistance and enhance injectability. Transitioning from 29-gauge to 27-gauge needles reduced glide force by 59 % (32 N → 13 N) during administration of 1 mL 20-centipoise viscous fluid (10 s injection), demonstrating enhanced injectability of high-viscosity formulations. Furthermore, a simulated human factors study with a diverse cohort (n = 12) evaluated the usability of the optimized device. A reduction in glide force correlates with an improvement in user perception and usability. Collectively, these combined studies provide practical, patient-centric design strategies to advance PFS injectability, linking technical optimization with real-world usability requirements.