These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

The understanding of resuspension in the pharmaceutical industry has been limited for some time. Classically, suspension style drugs have been transported in a vial then resuspended and delivered by a Health Care Professional (HCP). The arduous process involves adding fluid to a vial with a syringe, shaking the vial to achieve resuspension, using a new syringe to extract the resuspended drug before quickly injecting into the patient. The latest trend is to enable injections at home to drive down reliance on HCPs, which means that suspension drugs are now being added to the Pre-Filled Syringes (PFS) inside autoinjectors (similar to an EpiPen). Patients must shake their devices to resuspend the drug prior to self-injection. A simulation methodology has been developed that takes real-world inputs from a sensorised device containing an Inertial Measurement Unit (IMU) which has been shaken by human participants. The accelerations captured on the physical devices are ported into a CFD simulation as boundary conditions, which has a N-S Volume of Fluid (VOF) approach deployed to simulate bubble movement accurately. The rheological properties of these drugs are extremely complex and are typically shear thinning. Simulating the complete resuspension process using particles is unrealistic due to computational expense. Therefore, a novel lightweight methodology has been generated which enables the prediction of suspension dilution/transfer, and the subsequent variation of shear-dependent viscosity driven by the local concentration of the suspension. The presentation will showcase the novel modelling technique and use high-speed footage of shaking to provide verification of the approach. The technique developed is used to assess a novel resuspension technique that relies on high-accelerations generated by a device to propel a bubble into a bed of unsuspended powder and achieve resuspension without the need to manually shake the device; this approach demonstrates the ability to use the methodology to explore new patient-centric medical devices without having to physically prototype components first.