Design of xerogel pill with good swallowing performance through wet milling and drop freeze-drying processes

A novel dosage form with dose-adjusting and swallow-assisting functions, named "xerogel pills," was developed for pediatric or geriatric patients. It is a multiple-unit dosage form in which a single dose is divided into several pills. The pills are double-structured small spheres with an inner drug core and an outer dried-gel layer (xerogel shell). In this research, the preparing method (formulation and process) of the xerogel pills was established by using a combination of wet-milling and drop freeze-drying (DFD) techniques. Fexofenadine hydrochloride (FXF) was used as a poorly water-soluble model drug. Xanthan gum (XG), a gelling agent, was formulated to attain a smooth and soft mouth-feeling. The internal fluid consisting of the FXF nanosuspension prepared through the wet-milling process and the external fluid consisting of an XG solution were separately fed to a two-fluids nozzle composed of central and peripheral nozzles. Both fluids were concentrically dropped together into liquid nitrogen to construct double-structured droplets. After the freeze-drying process, the xerogel pills were formed. Mannitol (MNT), as a filler, was co-formulated with both fluids to strengthen the pills physically. The resultant pills were around 5-6 mm in diameter with a spherical shape, uniform size, and low density, enabling them to be easily swallowed, and quickly gelled upon contact with water. The FXF amount in one pill was 7-9 mg, depending on the XG loading in the external fluid. The relative standard deviation (RSD) of the FXF amount were varied in the range of around 3-10%, suggesting that the content uniformity would be acceptable as a composite dosage unit containing five or more pills. It was assumed that further improvements of the physical strength and drug content uniformity would be required to introduce the xerogel pills to practical use.