title: Comparative study of in vitro release and mucoadhesivity of gastric compacts composed of multiple unit system/bilayered discs using direct compression of metformin hydrochloride.
abstract: BACKGROUND
  Metformin is an oral anti-diabetic drug in the biguanide class. The goal of this study was to develop gastric-retentive MH discs in order to prolong the retention of drug in gastric mucosa.
  
  
  METHODS
  Two groups of metformin hydrochloride (MH) mucoadhesive gastroretentive discs were prepared: (a) bilayered discs prepared by direct compression of powders containing polymers as Carbopol 934P (CP, mucoadhesive polymer) and ethylcellulose (EC, rotardant polymer), (b) multiple unit system (microparticle) discs prepared by the emulsification, solvent evaporation, and compression technique from microparticles using polymers CP and EC. Gastric-mucoadhesive compacts were evaluated by investigating their release pattern, swelling capacity, mucoadhesion property, surface pH, and in vitro gastro-retentive time. Discs formulation was subjected to disintegration and dissolution tests by placing in 0.1 M hydrochloric acid for 8 h.
  
  
  RESULTS
  The production yield showed F2 microparticles of 98.80%, mean particle size of 933.25 µm and loading efficiency of 98.44%. The results showed that prepared microparticle discs had slower release than bilayered discs (p>0.05). The bilayered discs exhibited very good percentage of mucoadhesion. The results also showed a significant higher retention of mucoadhesive bilayered discs in upper gastrointestinal tract (F´1, 1:2 ratio of CP:EC). Histopathological studies revealed no gastric mucosal damage.
  
  
  CONCLUSIONS
  Mucoadhesive multiple unit system/bilayered discs interact with mucus of gastrointestinal tract and are considered to be localized or trapped at the adhesive site by retaining a dosage form at the site of action as well as improving in the intimacy of contact with underlying absorptive membrane to achieve a better therapeutic performance of anti-diabetic drug.
authors.affiliation: Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran ; Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Jelvehgari
authors.affiliation: Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran ; Liver and Gastrointestinal Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Parvin
authors.initials: P
authors.lastname: Zakeri-Milani
authors.affiliation: Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Khonsari
keywords: Bilayered discs; Carbomer 934P; Ethylcellulose; Metformin hydrochloride; Multiple unit system discs