title: [A comparative analysis of the influence of different types of Carbopol on the release rate of lithium-carbonate from matrix tablets].
abstract: OBJECTIVE
  Hydrophilic matrix tablets represent the most commonly used oral dosage form. Carbomers used in the concentration of 10%-30% for preparation of matrix tablets, may significantly affect the profile of drug release due to the formation of hydrogel matrix tablets. The aim of this study was to compare the influence of different types of Carbopol (carbomers in the pharmacopoeia) on the release rate of lithium-carbonate and other pharmaceutical, technological, physical and chemical properties of the prepared formulations of matrix tablets.
  
  
  METHODS
  Three different formulations of matrix tablets were made according to direct compression method. The tablets were of the following composition: carbomer, lactose monohydrate, magnesium-stearate, lithium-carbonate in the proportion 75:120: 5 : 300. The first formulation was made with Carbopol 971P NF, the second one with Carbopol 974 P NF and the third one with Carbopol 71G NF. The quantity of lithium-carbonate was determined according to the BP 2009, pharmaceutical and tecnological properties were examined in accordance with the regulations of Ph. Jug. V, whereas the release rate of lithium-carbonate from the formulations was examined by the application of dissolution test, prescribed in the monography 'Lithium Carbonate Extended-Release Tablets' in USP 26.
  
  
  RESULTS
  The profile of lithium-carbonate release from matrix tablets with Carbopol 974P NF entirely complies with the regulations of USP 26, whereas the values obtained from the analysis of matrix tablets with Carbopol 971P NF and Carbopol 71G NF were considerably lower than the prescribed ones. In all the investigated formulations the content of the drug, mass variation and tablet hardness comply with the regulations set in pharmacopoeia.
  
  
  CONCLUSIONS
  In the formulation of matrix tablets with lithium-carbonate, by the application of carbomers in the concentration of 15%, with Carbopol 974 P NF a favourable lithium-carbonate release profile was achieved, whereas in the formulations with Carbopol 971P NF and Carbopol 71G NF, the release rate was significantly lower than that given in the USP 26 monography.
authors.affiliation: Sektor za farmaciju, Vojnomedicinska akademija, Beograd, Srbija. marijat@yahoo.com
authors.forename: Marija
authors.initials: M
authors.lastname: Toskić-Radojcić
authors.forename: Marija
authors.initials: M
authors.lastname: Pavlović
authors.forename: Emilija
authors.initials: E
authors.lastname: Gazikalović
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Arandjelović
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Kovacević
mesh_terms: D000180:Acrylic Resins; D002626:Chemistry, Pharmaceutical; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005079:Excipients; D016651:Lithium Carbonate / Q000493:pharmacokinetics*; D011145:Polyvinyls; D013607:Tablets
chemical_list: D000180:Acrylic Resins; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005079:Excipients; D011145:Polyvinyls; D013607:Tablets; C006912:carboxypolymethylene; D016651:Lithium Carbonate