  Topical intra-nasal sprays are amongst the most commonly prescribed
therapeutic options for sinonasal diseases in humans. However, inconsistency
and ambiguity in instructions show a lack of definitive knowledge on best spray
use techniques. In this study, we have identified a new usage strategy for
nasal sprays available over-the-counter, that registers an average 8-fold
improvement in topical delivery of drugs at diseased sites, when compared to
prevalent spray techniques. The protocol involves re-orienting the spray axis
to harness inertial motion of particulates and has been developed using
computational fluid dynamics simulations of respiratory airflow and droplet
transport in medical imaging-based digital models. Simulated dose in
representative models is validated through in vitro spray measurements in
3D-printed anatomic replicas using the gamma scintigraphy technique. This work
breaks new ground in proposing an alternative user-friendly strategy that can
significantly enhance topical delivery inside human nose. While these findings
can eventually translate into personalized spray usage instructions and hence
merit a change in nasal standard-of-care, this study also demonstrates how
relatively simple engineering analysis tools can revolutionize everyday
healthcare.
