Impact of excipient composition and environmental humidity on the physicochemical properties of ondansetron orally disintegrating tablets: experimental and molecular simulation study.

Orally disintegrating tablets (ODTs) are highly sensitive to environmental humidity due to their hydrophilic excipients, which impact critical quality attributes like hardness, friability, and disintegration time. This study integrates molecular simulation with experimental analysis to investigate how excipient composition governs the moisture affinity and physicochemical stability of two ondansetron ODT formulations (gelatin-based vs. microcrystalline cellulose (MCC)-based) under varying humidity conditions. Molecular dynamics simulations predicted higher hygroscopicity for the MCC-based formulation, which correlated with experimental observations of increased friability and faster disintegration at elevated humidity. The gelatin-based formulation exhibited greater stability across humidity levels. These findings validate MD simulation as a predictive tool for screening excipient interactions with moisture during ODT pre-formulation. Molecular dynamics simulations were performed using Materials Studio 6.0.0 (BIOVIA, 2012) with the COMPASS force field. All molecular structures were energy-minimized, and amorphous cells for both formulations were constructed using the Amorphous Cell module with the COMPASS force field. Henry's constants and isosteric heats of adsorption were calculated using the Sorption module via Grand Canonical Monte Carlo simulations at 298 K. Experimental evaluations included hardness, friability, loss on drying, and disintegration time tests conducted according to USP 43-NF 38 guidelines at 29% and 57% relative humidity. Statistical analysis was performed using one-way ANOVA in JMP 13.2.0.