Colon-targeted delivery of niclosamide from solid dispersion employing a pH-dependent polymer via hotmelt extrusion for the treatment of ulcerative colitis in mice

Niclosamide (NCL) is repurposed to treat inflammatory bowel disease due to its anti-inflammatory properties and potential to reduce oxidative stress. This therapeutic activity remains challenging if administered directly due to its low solubility and high recrystallization tendency in gastric pH. Solid dispersions using pH-dependent polymer will be a better idea to improve the solubility, dissolution and targeted delivery at the colon. Hot melt extrusion was used to formulate a solid dispersion with 30% NCL utilising hydroxypropyl methylcellulose acetate succinate as a pH-dependent polymer. In vitro drug release studies revealed formulation (F1) containing 10%w/w Tween 80 showed minimal release (2.06%) at the end of 2 h, followed by 47.87% and 82.15% drug release at 6 h and 14 h, respectively, indicating the maximum amount of drug release in the colon. The drug release from the formulations containing no plasticiser and 5%w/w plasticiser was comparable to the pure crystalline drug (approximately 25%). Solid-state analysis confirmed particle conversion of crystalline NCL to amorphous form, and the optimised formulation was stable for 6 months without significant changes in dissolution profile. In contrast to pure NCL, the F1 formulation substantially reduced the disease activity index, colonic inflammation, histological alterations and oxidative damage in colitis mice. These findings reveal that the prepared formulation can potentially deliver the drug locally at the colon, making it an effective tool in treating ulcerative colitis.