Nasal and MDI suspensions that contain insoluble excipients in addition to the API present a special challenge for product developers who need to determine the particle size distribution of the API. While the pharmaceutical industry has had a number of well-established methods for determining the particle size distribution (PSD) of a drug in orally inhaled and nasal drug products (OINDPs), particularly cascade impaction, those methods cannot differentiate between ingredients. If the PSDs of the API and an excipient overlap, accurately determining the PSD of the API becomes impossible with standard instruments.
Ingredient-specific particle sizing
This article describes a technique using a combination of Raman chemical imaging and optical microscopy that allows product developers to obtain particle size distributions of both API and excipient in a suspension.