The use of a pH-dependent and Non pH-dependent Natural Hydrophobic Biopolymer (Landolphia owariensis latex) as Capsule Coating Agents in in vitro Controlled Release of Metronidazole for Possible Colon Targeted Delivery

N C Obitte, A Chukwu, I V Onyishi


Summary: Orally administered metronidazole often requires just a fraction of the administered dose for optimum local activity in the colon. Any formulation design that can target drug to the colon may require dose reduction while improving therapeutic activity. Colon targeted drug delivery achieves this fit. The objective of this work therefore was to evaluate the in vitro effect of, the percentage of surface area of capsule surface coated with Landolphia owariensis latex (LOL), particle size of granules, and %w/w of matrix former (methylcellulose) on the release of metronidazole from coated hard gelatine capsules for possible delivery to the colon. Metronidazole granules were prepared by the wet granulation technique and appropriately encapsulated prior to primary coating of capsule with Eudragit® L-100 and secondary coating with LOL. Capsules having primary coating of Eudragit® L-100 were coated with LOL atop 50% or 85% capsule surface. In vitro drug release was carried out sequentially in media of pH 1.2(0.1N HCl), 6.8 and 7.4(phosphate buffer solution) respectively. The dissolution data were subjected to kinetic treatment. Results showed that the greatest quantity of drug release took place at pH 7.4 over 9-20 h. Univariate analysis of variance indicated that surface area of capsule coated with LOL had a significant (p<0.05) effect on both amount of drug released and time of release at pH 7.4.Matrix former concentration also significantly (p<0.05) affected the quantity of drug released and time of release (T7.4) at pH 7.4. Most of the capsules prepared with 4% methylcellulose had better fit than those of 1% on the applied kinetic models. Capsules with 85% surface coated with LOL recorded higher dissolution efficiency (DE) and mean dissolution time (MDT) values, except in a few cases. Landolphia owariensis latex, has therefore proved to be a potentially useful polymer for possible achievement of colon targeted drug delivery.

Industrial relevance: Landolphia owariensis latex is an ignored part of the climber tree. It can be cultivated and tapped to commercial scale as in rubber. There is presently a patent based on colon targeted technology which adopted  capsule coating approach. The dip method of coating employed in this article is a common technology in capsule manufacture; therefore coating of the capsules with our natural biopolymer and Eudragit L-100 is not going to be tasking. This double hydrophobic coating technique prolongs drug release enough to convey the capsule to the colon with greatest quantity of the drug intact. This makes colon drug targeting an attractive drug delivery approach for the rare oral delivery of protein/biotech products, etc. Insulin is commonly presented as an injectable with its attendant problem of patient compliance and frequent puncturing of the skin. With capsule filling machines having coating accessories attached to them large scale manufacture can be embarked upon.


Landolphia owariensis; Metronidazole; Colon targeting; Eudragit® L-100; Controlled drug release

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