Evaluation of the mechanical properties and drug release of cross-linked Eudragit films containing metronidazole.

The mechanical properties of casted Eudragit E-100 films were tested for the combined effect of two cohesion promoters (succinic or citric acid) and triacetin as a plasticizer. The prepared films were elastic, self-adhesive, transparent and pale yellow in colour. Films containing either of the tested cohesion promoters showed a significant reduction in both tensile strength and Young's modulus on increasing triacetin and/or cohesion promoter concentration. Films containing 7% (w/w) succinic acid and 45% (w/w) triacetin gave the highest elongation of the tested films at any given stress with a maximum of 1050% elongation. Optimal bonding to human skin surface (tack) with the highest peel adhesion (588 cN/cm) was observed with these films denoting good self-adhesive properties. In vitro metronidazole (MN) release from the plasticized Eudragit E-100 films was monitored for the influence of incorporation of cohesion promoters, secondary polymer (Eudragit RL or RS) as well as drug loading. Both cohesion promoters were seen to improve MN release from the films with the maximum drug flux (0.334 mg cm(-2) h(-1)) observed with 1.75% (w/w) succinic acid. The tested secondary polymers were also found to improve MN release from the tested films. The highest MN release was observed with 20% (w/w) Eudragit RL which gave 0.77 mg cm(-2) released after 3 h compared with only 0.34 mg cm(-2) for plain films. MN release from the films was increased by increasing drug load. Calculating the release rate constant (K(r)) showed a linear increase with the increase in drug load.