Evaluation of the impact of viscosity, injection volume, and injection flow rate on subcutaneous injection tolerance.

Aim: The primary objective of this study was to evaluate the impact of fluid injection viscosity in combination with different injection volumes and flow rates on subcutaneous (SC) injection pain tolerance.

Methods: The study was a single-center, comparative, randomized, crossover, Phase I study in 24 healthy adults. Each participant received six injections in the abdomen area of either a 2 or 3 mL placebo solution, with three different fluid viscosities (1, 8-10, and 15-20 cP) combined with two different injection flow rates (0.