From actuation to deposition: Particle sizing techniques for characterizing nasal drug delivery systems

In its draft guidance “Bioavailability and Bioequivalence Studies for Nasal Aerosols and Nasal Sprays for Local Action” (April 2003),⁴ the FDA highlights the use of laser diffraction for measurement of the particle size distribution of both nasal sprays and nasal aerosols. Cascade impaction is recommended for scrutiny of the finer end of the distribution. This article examines these two complementary techniques, explains in some detail how they work and shows how they can be applied in tandem to deliver valuable information for nasal product characterization.