Taste-Masked Diclofenac Sodium Microparticles Prepared by Polyelectrolyte Complexation: Formulation Using Different Fatty Acids and Taste Evaluation by Human Panel

Background/Objectives: Paediatric patients continue to lack access to age-appropriate oral medicines for their treatment and have to depend on the off-label use of medicines approved for adults, which compromises dosing accuracy and exposes children to unpleasant bitterness. Building on previous proof-of-concept work with flucloxacillin sodium, this study investigated the effects of fatty-acid chain length on the formation, stability, dissolution, and sensory acceptability of diclofenac sodium (DS)–Eudragit® EPO (EE)–fatty acid (FA) polyelectrolyte complexes (PECs). Four saturated fatty acids, lauric (C12), myristic (C14), palmitic (C16), and stearic acid (C18), were evaluated at stoichiometric equimolar DS:EE:FA ratio (1:1:1). Methods: PEC microparticles were prepared by solvent evaporation. A stability-indicating RP-HPLC assay was developed and validated according to ICH guidelines to quantify DS content. Drug content and stability were monitored over 3 months at ambient storage. In vitro dissolution was performed in pH 5.5 medium at 37 °C. Taste acceptability and willingness to take again was assessed with 25 healthy adult volunteers using 11-point scale. Results: All PECs retained >90% of expected drug content after 3 months. Compared with neat DS, PECs markedly suppressed early drug release (32–39% vs. 94% at 2 min) but achieved >87% cumulative drug release in 60 min. Sensory evaluation showed significant differences across samples (p < 0.001): neat DS was least acceptable (20.8% willing to take again), while DS-EE-PA was most acceptable (92%), followed by DS-EE-SA and DS-EE-MA. DS-EE-LA was least favoured among PECs. Conclusions: Fatty-acid chain length influenced PEC formation and taste acceptability, but not the PEC stability and drug dissolution profile. Palmitic acid (DS-EE-PA) offered the best overall profile and represents a promising candidate for further development of paediatric-appropriate diclofenac formulations.