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Updated: Apr 25, 2026

The Quantification of Injectability by Mechanical Testing
Published on: May 13, 2020
Model study of the pressure build-up during subcutaneous injection
Maria Thomsen1, Anier Hernandez-Garcia2, Joachim Mathiesen2
1Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; Novo Nordisk A/S, Hillerød, Denmark.
Abstract:
In this study we estimate the subcutaneous tissue counter pressure during drug infusion from a series of injections of insulin in type 2 diabetic patients using a non-invasive method. We construct a model for the pressure evolution in subcutaneous tissue based on mass continuity and the flow laws of a porous medium. For equivalent injection forces we measure the change in the infusion rate between injections in air at atmospheric pressure and in tissue. From a best fit with our model, we then determine the flow permeability as well as the bulk modulus of the tissue, estimated to be of the order 10-11-10-10 m2 and 105 Pa, respectively. The permeability is in good agreement with reported values for adipose porcine tissue. We suggest our model as a general way to estimate the pressure build-up in tissue during subcutaneous injection.
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