Injection pads serve a critical role in the development of injectable drug-device combination products (e.g. pre-filled syringes, autoinjectors) by mimicking the human skin during a subcutaneous injection. These pads are used in Human Factors Engineering/Usability studies with patients, as well as in design verification studies to assess device performance. An acceptable injection pad should be made of suitable materials so that the back pressure during injection is similar to that in human tissue. Unfortunately, there is limited information in the literature about commercially available injection pads with regards to their ability to mimic tissue back pressure.<br/><br/>This study used a pig tissue model since this is the most representative animal model for human skin. The pig model included pork shoulder cuts that were fresh from slaughter. Each pork shoulder cut maintained the relevant tissue layers intact, i.e. skin, subcutaneous tissue, and underlying muscle tissue. The test injections were conducted using a pre-filled syringe that delivered a 2 mL volume of a model formulation of a monoclonal antibody. The syringes were tested using Instron force measurement equipment to measure the break-loose and glide force profiles during injection at a constant compression rate. The injections were performed into air, multiple test pads, and pork shoulder with a sample size of 30 each.<br/><br/>The results identified a suitable injection pad(s) for which there was no statistically significant difference in the force profiles between the pad and pork tissue. However, there was a statistically significant difference for injections into air, which confirms the additional back pressure from pad/tissue. This study also highlights a technique to determine the acceptability of injection pads used in injectable drug delivery device development.

Assessment of subcutaneous injection pads as acceptable skin mimics

249th National Meeting (2015)

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