title: Development of modified in situ gelling oral liquid sustained release formulation of dextromethorphan.
abstract: BACKGROUND
  Alternative strategies are being employed to develop liquid oral sustained release formulation. These included ion exchange resin, sustained release suspensions and in situ gelling systems. The later mainly utilizes alginate solutions that form gels upon contact with calcium which may be administered separately or included in the alginate solution as citrate complex. This complex liberates calcium in the stomach with subsequent gellation. The formed gel can break after gastric emptying leading to dose dumping.
  
  
  OBJECTIVE
  Development of modified in situ gelling system which sustain dextromethorphan release in the stomach and intestine.
  
  
  METHODS
  Solutions containing alginate with calcium chloride and sodium citrate were initially prepared to select the formulation sustaining the release in the stomach. The best formulation was combined with chitosan. All formulations were characterized with respect to flow, gelling capacity, gelling strength and drug release.
  
  
  RESULTS
  Increasing the concentration of alginate increased the gelling capacity and strength and reduced the rate of drug release in gastric conditions with 2% w/v alginate being the best formulation. However, these formulations failed to sustain the release in the intestinal conditions. Incorporation of chitosan with alginate increased the gelling capacity and strength and reduced the rate of drug release compared to alginate only system. The effect was optimum in formulation containing 1.5% w/v chitosan. The sustained release pattern was maintained both in the gastric and intestinal conditions and was comparable to that obtained from the marketed product.
  
  
  CONCLUSIONS
  Alginate-chitosan based in situ gelling system is promising for developing liquid oral sustained release.
authors.affiliation: Department of Pharmaceutical Technology, College of Pharmacy, University of Tanta, Egypt. gmmelmag@yahoo.com
authors.forename: Gamal M
authors.initials: GM
authors.lastname: El Maghraby
authors.forename: Ehab M
authors.initials: EM
authors.lastname: Elzayat
authors.forename: Fars K
authors.initials: FK
authors.lastname: Alanazi
mesh_terms: D000284:Administration, Oral; D000464:Alginates / Q000737:chemistry; D002122:Calcium Chloride / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods; D048271:Chitosan / Q000737:chemistry; D002951:Citrates / Q000737:chemistry; D003692:Delayed-Action Preparations; D003915:Dextromethorphan / Q000008:administration & dosage / Q000737:chemistry*; D005753:Gastric Mucosa / Q000378:metabolism; D005782:Gels / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D019999:Pharmaceutical Solutions / Q000008:administration & dosage / Q000737:chemistry*; D000077559:Sodium Citrate; D014783:Viscosity
chemical_list: D000464:Alginates; D002951:Citrates; D003692:Delayed-Action Preparations; D005782:Gels; D006603:Hexuronic Acids; D019999:Pharmaceutical Solutions; D000077559:Sodium Citrate; D003915:Dextromethorphan; D020723:Glucuronic Acid; D048271:Chitosan; D002122:Calcium Chloride