29. Betageri, Guru V.; Deshmukh, Deepali V.; Gupta, Ram B.  Oral sustained-release bioadhesive tablet formulation of didanosine.    Drug Dev. Ind. Pharm.  (2001), 27(2),  129-136.


The objective of this study was to formulate a hydrogel-forming bioadhesive drug delivery system for oral administration of didanosine (DDL).  The aim of this tablet dosage form was to improve the oral absorption of DDL by delivering it in small doses over an extended period and localizing it in the intestine by bioadhesion.  Compressed tablets of DDL by using Polyox WSRN-303, Carbopol 974P-NF, and Methocel K4M as the bioadhesive release rate-controlling polymers were prepd.  The effect of polymer concn. on the release profile and in vitro bioadhesion of the matrix tablets was studied.  Tablet formulations with Polyox WSRN-303 (10%) and Methocel K4M (30%) showed 93 and 90% drug release, resp., after 12 h.  The drug release was linear when fitted in the Higuchi equation (square-root time equation), suggesting zero-order release.  Carbopol 974P inhibited the complete release of DDL because of drug-polymer interaction; hence, is not suitable for formulation of DDL.  Drug diffusion and swelling of the polymer (anomalous Fickian release) was dominant in DDL release.  In general, in vitro bioadhesion increased with an increase in polymer concn.  Tablets contg. a single polymer can be designed to form hydrogels serving the dual purpose of bioadhesion and sustained release.


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