Febuxostat Self-Emulsifying Drug Delivery System: Formulation and In-Vitro Characterization

Background: Febuxostat is a non-purine xanthine oxidase inhibitor used for chronic hyperuricaemia in gout. It is practically insoluble in water and behaves as a BCS class II compound, so its dissolution from conventional tablets can be slow and variable. Objective: To develop a liquid self-emulsifying drug delivery system (SEDDS) of febuxostat from lipidic excipients and to compare it's in vitro dissolution with commercially available febuxostat tablets. Methods: Oils, surfactants and co-surfactants were screened by drug solubility and percentage transmittance. Seven liquid SEDDS (F1–F7) were prepared with Caproyl (propylene glycol monocaprylate) as oil, Acrysol K 160 as surfactant and Transcutol P as co-surfactant, and one comparator (O1) with oleic acid as oil. All contained 40 mg febuxostat. The formulations were evaluated for self-emulsification time, robustness to dilution, transmittance, drug content, FT-IR compatibility and dissolution in 900 mL phosphate buffer (pH 6.0). Profiles were compared with four marketed 40 mg tablets (A–D) using dissolution efficiency (DE₆₀), the difference factor (Fd) and the similarity factor (Fs). Results: A UV method at 314 nm was linear from 2 to 12 µg/mL (R² = 0.9963) and precise (RSD 0.77%). Febuxostat was most soluble in Acrysol K 160 (100 mg/mL), Caproyl (66.7 mg/mL) and Transcutol P (66.7 mg/mL). All formulations emulsified within 21 s and showed no phase separation at 1:50 to 1:500 dilutions in water, pH 6.0 buffer or 0.1 N HCl. F7 (Caproyl:Acrysol K 160:Transcutol P, 2.1:2:1 w/w) emulsified fastest (13 s), had the highest transmittance (98.7%) and a drug content of 98.95%, and released 97% of the drug at 60 min. The marketed tablets released 32.5–77.1% over the same period. F7 had the highest DE₆₀ (61.8%), and its Fs values against the four tablets (17.0–43.6) confirmed that its profile was different from, and higher than, the commercial products. The oleic acid system released only 12.9%. Conclusion: A Caproyl/Acrysol K 160/Transcutol P SEDDS markedly improved the in vitro dissolution of febuxostat over marketed tablets. Droplet size, stability and in vivo studies are needed before any claim on bioavailability can be made.