title: Oral-based controlled release formulations using poly(acrylic acid) microgels.
abstract: OBJECTIVE
  To investigate the release of hydrophobic and hydrophilic substances from tablets containing Pemulen and Carbopol as excipients.
  
  
  METHODS
  The dissolution patterns of a hydrophobic (diazepam) and a hydrophilic active substance (midodrine-HCl) from different tablet formulations containing a nonmodified polyacrylic microgel (Carbopol 981 F) or a hydrophobically modified polyacrylic microgel (Pemulen) have been studied. Possible differences in dissolution in phosphate buffer (pH 6.8) and in 0.1 M HCl between tablets produced using wet granulation and direct compression were also investigated.
  
  
  RESULTS
  Tablets produced by wet granulation had a greater effect on the release of active substance from the tablets. No major differences were observed in the release patterns of the hydrophilic substance midodrine-HCl from wet granulated tablets based on Carbopol and Pemulen. However, the release pattern of the more hydrophobic drug substance, diazepam, differed considerably between the two polymers. Wet granulation gave reproducible release patterns. The release patterns from the polymers differed considerably at pH 6.8 but were similar at low pH.
  
  
  CONCLUSIONS
  The release of the diazepam from the hydrophobic polymer Pemulen was very slow, and the release was close to zero order.
authors.affiliation: Division of Food Technology, Department of Food Engineering, Lund University, Lund, Sweden. marie.wahlgren@food.lth.se
authors.forename: Marie
authors.initials: M
authors.lastname: Wahlgren
authors.forename: Karin Löwenstein
authors.initials: KL
authors.lastname: Christensen
authors.forename: Erik Valentin
authors.initials: EV
authors.lastname: Jørgensen
authors.forename: Anna
authors.initials: A
authors.lastname: Svensson
authors.forename: Stefan
authors.initials: S
authors.lastname: Ulvenlund
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000284:Administration, Oral; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000737:chemistry; D003692:Delayed-Action Preparations; D003975:Diazepam / Q000008:administration & dosage* / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry*; D005782:Gels; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000737:chemistry; D008879:Midodrine / Q000008:administration & dosage* / Q000737:chemistry; D012995:Solubility; D013607:Tablets
chemical_list: D000180:Acrylic Resins; D000316:Adrenergic alpha-Agonists; C516894:Carbopol 981; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005782:Gels; D006993:Hypnotics and Sedatives; D013607:Tablets; C006903:carbopol 940; D008879:Midodrine; D003975:Diazepam