Melt-Filled Hard Capsules as an Applicable Compounding Strategy to Enhance the Dissolution of Poorly Water-Soluble Nifedipine Using Polyethylene Glycol Matrices

Background/Objectives: Poor aqueous solubility limits the oral absorption and bioavailability of many active pharmaceutical ingredients. Simple formulation approaches suitable for hospital and community pharmacy compounding are therefore needed. This study aimed to develop and evaluate melt-filled hard capsules containing nifedipine, a model of poorly water-soluble BCS class II drug, using polyethylene glycol (PEG) carriers to improve dissolution performance. Methods: PEG blends of different molecular weights (PEG 400, PEG 1500, and PEG 4000) were prepared by melt mixing, followed by incorporation of nifedipine and manual filling into hard gelatin capsules. The formulations were characterized regarding mass variation, drug content, in vitro dissolution, rheological behavior, and solid-state properties using Fourier transform infrared (FTIR) spectroscopy. Dissolution profiles were kinetically modeled and compared with pure nifedipine. Results: All capsules met pharmacopoeial requirements for mass uniformity and showed acceptable drug content. PEG-based melt-filled formulations exhibited markedly enhanced dissolution compared with crystalline nifedipine. Faster drug release was associated with lower-molecular-weight PEGs and reduced viscosity, with the PEG 400/PEG 1500 blend demonstrating the most rapid dissolution. Rheological analysis confirmed shear-thinning behavior, while FTIR findings suggested intermolecular interactions and partial amorphization of nifedipine within the PEG matrices. Conclusions: This study provides a translational adaptation of solid dispersion principles into a compounding-compatible melt-filling approach.