Development and optimization of an oral vitamin D3 microemulsion with enhanced anti-inflammatory activity in a carrageenan-induced paw edema model

One of the most prevalent types of arthritis in the globe is osteoarthritis and rising due to aging populations and increased obesity rates. The vitamin D3 offered anti-inflammatory and chondroprotective properties, making it a potential therapeutic option for osteoarthritis. This study aimed to develop an oral microemulsion of vitamin D3 that enhances anti-inflammatory activity in a carrageenan-induced paw edema model for the preliminary screening in the therapy of osteoarthritis. The microemulsion was prepared by water titration method and was statistically optimized with the help of D-optimal mixture design considering concentration of oil, Smix and distilled water as independent responses and % transmittance and globule size as dependent responses. The optimized microemulsion was transparent (100.10 ± 0.15% transmittance), with a globule size of 22.88 ± 2.64 nm, polydispersity index of 0.216 ± 0.081, zeta potential of −8.946 mV ± 1.152, pH 7.10 ± 0.08, viscosity of 117 ± 15 cp and drug content of 98.27 ± 0.78%. Transmission electron microscopy represented spherical morphology with an even surface. Stability study demonstrated satisfactory results under various atmospheric conditions. In vitro drug release from microemulsion showed sustained release of 95.87 ± 3.46% of drug for 8 hours in comparison to 93.12 ± 2.17% release in marketed soft gelatin capsule in 2 hours. The vivo study performed in a carrageenan-induced paw edema model showed substantial anti-inflammatory properties in wistar rats compared to marketed standard preparations. Henceforth, it can be concluded that the developed vitamin D3 microemulsion holds potential for enhancing anti-inflammatory activity in an acute inflammation model and is a promising candidate for further testing in osteoarthritis models.