Assessment of Mass Fraction Less Than 10 micron in Nasal Products – Method Considerations

Niklas Baltz and Regina Scherließ

Department of Pharmaceutics and Biopharmaceutics, Kiel University, Grasweg 9a, 24118 Kiel, Germany


Nasal products may contain inhalable droplets or particles smaller than 10 microns. With rising interest in using the nasal application route for systemic treatment, e.g. for diseases of the central nervous system, the safety of the route needs to be further assessed. Those small droplets or particles may transport drugs and excipients to the lungs where their risk profile is unknown or negative. Hence, a fast and easy method for determining the mass fraction less than 10 micron is needed. Different setups were assessed using a commercially available and locally acting nasal spray for allergy treatment. Different impactors and inlets were tested. The Fast Screening Impactor provided the best results with a high recovery and low standard deviation. Further experiments with suspension, dry powder and nasal metered dose formulations will be conducted to optimise and validate the preferred method.

Key Message

For the assessment of the inhalable mass fraction less than 10 micron in nasal sprays, the Fast Screening Impactor is generally suitable. As shown in this study, the choice of the inlet influences the results and therefore needs to be reported. Mandatory prerequisites are an analytical method with low quantification limit and precisely determined emitted dose.