Application of the literature-derived modified penetration model to quantify drug particle depth in the viable epidermis post-stratum corneum transit

Purpose This study aims to determine the powdered drug penetration depth delivered by means of a micro-shock tube-based needle-free drug delivery device based on a literature-derived modified penetration model. Design/methodology/approach A two-dimensional transient compressible particle-gas flow simulation was done using ANSYS Fluent. The discrete phase model simulates drug particle behaviour in a continuous gas phase. Several pressure ratios (PRs) were used in the quantitative study. The nozzle exit pressure and particle velocity were validated against experimental results. Using modified mathematical formulae from the literature, particle or powder penetration depth, Mach number, vorticity and the effect of PRs on flow are examined to understand penetration depth changes. Findings By changing the PRs from 9 to 60, the penetration depth was investigated on the basis of particle velocity that was varied from 47 to 179 m/s obtained at different PRs. Using a modified model found in the literature, this penetration depth result has been used to examine the impact of the PRs on the penetration depth. After careful computation, the authors discovered that the penetration depth was marginally impacted between PR = 40 and 60. Penetration depth at PR = 40 and 60 was around 0.053 and 0.057 mm. Originality/value Considering the particle velocity at the stratum corneum–viable epidermis boundary, the particle penetration depth at various PRs for drug delivery using a needle-free device is crucial but rarely studied. Some helpful information for drug distribution using a needle-free device is provided by the current numerical workflow.