The synergistic effect of Landolphia owariensis latex and Eudragit® L-100-coated capsules on the in vitro controlled release of metronidazole for possible colon targeting

Abstract

The overall objective of this present investigation was to determine the synergistic potentiality of Landolphia owariensis latex (LOL) and Eudragit® L-100 as hydrophobic polymeric agents in ensuring controlled drug release for possible colon-targeted delivery of metronidazole. Metronidazole granules were prepared by the wet granulation method and manually encapsulated. The entire capsule surface was first coated with Eudragit® L-100 (primary coating). Secondly half (50%) or five-sixth (5/6 or 83%) of the capsule surface was coated atop the primary coating with LOL (secondary coating). Two different granule size fractions were isolated and compared. Parallel gradient in vitro drug release studies were carried out in media of pH 1.2, 6.8 and 7.4, respectively. The dissolution data were subjected to kinetic treatment. Results showed that the least quantity of drug release took place at pH 1.2 followed by pH 6.8, with greatest drug release taking place at pH 7.4. Capsule surface coated with LOL significantly (P<0.05) affected drug release and time of release. Matrix former(binder) concentration had no significant (P<0.05) effect on drug release, but particle size did. More than one drug release mechanisms were operational and most capsules with 50% surface coated with LOL recorded higher Dissolution efficiency (DE) but lower Mean dissolution time (MDT) than those of 83%. In conclusion, the use of Eudragit® L-100 and LOL as primary and secondary capsule coatings respectively have demonstrated competence in controlling drug release and thus may hold promise at preferentially targeting metronidazole to the colon against amebic diseases.