Rheological behavior of nasal sprays in shear and extension

Area of Science:

• Rheology
• Pharmaceutics
• Nasal Drug Delivery

Background:

• Corticosteroid nasal sprays are widely used for rhinitis.
• Understanding their rheological properties is crucial for effective nasal drug delivery.
• Previous studies have not fully characterized the rheology of leading commercial nasal spray suspensions.

Purpose of the Study:

• To compare the rheological profiles of four commercial corticosteroid nasal spray suspensions.
• To investigate the shear thinning and thixotropic behavior of these suspensions.
• To examine the extensional properties influencing droplet behavior and nasal residence time.

Main Methods:

• Rheological analysis using shear (flow curves, viscosity measurements) and extensional techniques.
• Utilized a Carri-Med CSL100 with concentric cylinder geometry.
• Employed digital photography to observe droplet evolution and filament formation during extrusion.

Main Results:

• All investigated nasal spray suspensions demonstrated shear thinning and varying degrees of thixotropy.
• Thixotropic recovery was minimal within 5 minutes, suggesting it's not the primary factor for nasal residence.
• High viscosity, even after structural breakdown, appears to be key for prolonged nasal residence.
• Extensional flow data revealed differences among sprays, correlating with low shear rate viscosities.

Conclusions:

• Commercial corticosteroid nasal sprays exhibit complex rheological behaviors.
• High viscosity is a more significant factor than thixotropy for nasal residence time.
• Differences in extensional properties may influence droplet breakup and deposition, warranting further investigation.