The objective of this study was to develop a dry powder coating technique applied to colon targeting tablets containing metronidazole (MET) by using a pan coater. The coating formulation consisted of a polymer mixture (pectin/HPMC) and plasticizer (dibutyl phthalate). Dissolution rate of MET was conducted at pH 1.2, 7.4 and 6.8 in the presence of pectinolytic enzyme. The lag time release of MET was simultaneously controlled by enzyme signal in colonic medium and coating level. There was a significant correlation between the coating level and lag time release when the ratio of pectin: HPMC was from 1:1 to 3:1. 

Key words: dry powder coating; metronidazole; colon targeting tablet; pectin; HPMC; pectinolytic enzyme; excipient

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