Eudragit® and hydrotalcite-like anionic clay composite system for diclofenac colonic delivery

In this paper, the microencapsulation of the MgAl-hydrotalcite (HTlc) and diclofenac (DIK) intercalation product (HTlc-DIK) was realized in order to obtain a composite system for colonic drug delivery. Eudragit S or Eudragit L were used as polymers for preparation of microparticles (MPs). MPs were prepared by using a properly modified oil-in-oil solvent evaporation method. A 1:5 or 1:10 w/w HTlc-DIK/polymer ratios were employed. An experimental design was applied in order to assess the preparation variable effects on the qualitative MP appearance. Improved MP preparations were achieved when 7–13 ml of acetone-ethanol solution was employed at both HTlc-DIK/polymer ratios. The MPs were tested for in vitro drug release. DIK release from Eudragit L MPs at pH 6.8 reached 26–35% within 25–30 min at both HTlc-DIK/polymer ratios and no further increase was observed when the pH was shifted to 7.5. DIK release from Eudragit S MPs at pH 7.5 reached for both ratios 70% after 6–8 h. The obtained results showed that hydrotalcite intercalation compound can be microencapsulated without missing the intercalated compound and the resulted composite MPs showed good characteristics. Besides HTlc-DIK/Eudragit S MPs possess improved features with respect to HTlc-DIK/Eudragit L MPs. For this reason, HTlc-DIK/Eudragit S MPs could be promising for drug delivery either to the distal part of small intestine or to the colon.