Formulation of Self-Emulsifying Microemulsion for Acemetacin Using D-Optimal Design: Enteric-Coated Capsule for Targeted Intestinal Release and Bioavailability Enhancement

<b>Objectives</b>: The current work aimed to formulate and optimize a self-emulsifying microemulsion drug delivery system (SEME) for acemetacin (ACM) to increase ACM's aqueous solubility, improve oral bioavailability, and reduce gastrointestinal complications. <b>Methods</b>: Screening of components capable of enhancing ACM solubility was performed. Pseudo-ternary phase diagrams were performed to choose the optimal formulation ratio. The ACM-SEME formulation's composition was optimized using D-optimal design. Oil, S_mix, and water percentages were used as independent variables, while globule size, polydispersity index, ACM content, and in vitro ACM release after 90 min were used as dependent variables. Also, thermodynamic stability and transmittance percentage tests were studied. Zeta potential was assessed for the optimized ACM-SEME formulation, which was then subjected to spray drying. The dried ACM-SEME was characterized using field-emission scanning electron microscope, Fourier-transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry. The dried ACM-SEME formulation was filled into hard gelatin capsules and coated with Eudragit L100 to achieve pH-dependent release. <b>Results</b>: The antinociceptive activity of ACM-SEME was evaluated in vivo using Eddy's hot plate test in rats, revealing a significant prolongation of the noxious time threshold compared to control groups. Ex vivo permeation studies across rat intestinal tissue confirmed the enhanced permeation potential of the ACM-SEME. <b>Conclusions</b>: It was concluded that the developed ACM-SEME system demonstrated improved physicochemical properties, enhanced release behavior, and superior therapeutic performance, highlighting its potential as a safer and more effective oral delivery platform for ACM.