Statistical Formulation Optimization of Naproxen Microsponges with Eudragit RS100 for Sustained Drug Release

Abstract

Background and Objective

This study aims to address the solubility, stability, and bioavailability challenges of Naproxen, a widely used nonsteroidal anti-inflammatory drug (NSAID), by formulating Naproxen-loaded microsponges with controlled release properties. The ultimate objective is to achieve enhanced drug concentration in the bloodstream while ensuring prolonged therapeutic efficacy. Naproxen was specifically chosen for this study due to its frequent clinical use in managing musculoskeletal disorders, arthritis, and inflammatory conditions, along with its poor aqueous solubility (BCS Class II) and gastrointestinal side effects upon oral administration. While other NSAIDs, such as ibuprofen, diclofenac, and celecoxib, face similar biopharmaceutical limitations, Naproxen’s longer half-life and strong anti-inflammatory efficacy make it a suitable candidate for a controlled topical delivery system to enhance localized action, reduce systemic toxicity, and improve patient compliance.

Methods

Naproxen microsponges were developed using the quasi-emulsion solvent diffusion technique. Eudragit RS100 (ERS100) was employed as the polymer, polyvinyl alcohol (PVA) as the stabilizing emulsifier, and dichloromethane (DCM) as the organic solvent. To systematically optimize the formulation, a Box-Behnken design was utilized, enabling the evaluation of critical formulation and process parameters. The independent variables included ERS100 amount (X₁), PVA concentration (X₂), and stirring speed (X₃). Response factors were defined as particle size, percentage yield, and entrapment efficiency (%EE).

Results

All prepared microsponge batches demonstrated an initial burst release of more than 40% of Naproxen within the first hour, followed by a sustained drug release profile over 8 h. The optimized batch, identified through desirability-based software optimization, exhibited a particle size of 22.32 µm, a percentage yield of 85.14%, and an entrapment efficiency of 69.11%. Drug release from the optimized formulation (NXMF2) was found to follow the Korsmeyer-Peppas model, indicating a diffusion-controlled release mechanism.

This study demonstrates the potential of microsponge technology as an effective strategy to enhance the bioavailability and therapeutic performance of Naproxen, with the optimized formulation offering controlled release and improved pharmacokinetic properties.

Conclusion

The Naproxen-loaded microsponges achieved sustained drug release, improved bioavailability, and enhanced stability, demonstrating their potential for effective controlled drug delivery.