Design of a pH-responsive oral gel formulation based on the matrix systems of gelatin/hydroxypropyl methylcellulose phthalate for controlled drug release

Extensive efforts have been directed toward developing novel easily digested formulations with desirable controlled-release properties. The present study sought to develop pH-responsive oral gel formulations using combinations of gelatin and enteric polymers for controlled drug release under stimulated gastric conditions using acetaminophen and fluorescein isothiocyanate (FITC)-labeled dextran as model compounds.

Highlights

Gelatin/enteric polymer gels slowed the release of acetaminophen at pH 1.2.

The gelatin/HPMCP content in gels affected the textural properties.

FITC-dextran release decreased as the dextran molecular weight was increased.

Gelatin/HPMCP gels formed a matrix structure at pH 1.2.

Hydroxypropyl methylcellulose phthalate (HPMCP) was identified as the optimal excipient for the pH-responsive drug release system because the release rates of acetaminophen in gelatin/HPMCP gels at pH 1.2 were exceedingly lower than those in other polymer-containing gels. Texture profile analysis of gelatin/HPMCP gels revealed the optimal content of excipients concerning ingestibility. FITC-labeled dextran of varying molecular weights was used to investigate the mechanism of compound release from the gelatin/HPMCP system under acidic conditions. The release properties practically depended on the molecular weight of FITC-dextran, and the compound release rate was proportional to the square root of time. The matrix structures of gelatin/HPMCP gels at low pH offer advantageous pH-responsive drug release profiles. Continue on pH-responsive oral gel 

Keywords: Enteric polymer; FITC-dextran; Higuchi equation; pH-responsive release; Textural properties, Gelatin (Type B, 250 Bloom), Hydroxypropyl methylcellulose [HPMC, TC-5® (M.W. 22,000)], HPMCP (HPMCP®-55 (M.W. 84,000), HPMCAS [Shin-Etsu AQOAT® AS-LF (M.W. 18,000)],  Methacrylic acid-ethyl acrylate copolymer (Eudragit® L100-55 (M.W. 125,000)