title: Formulation development and in vitro evaluation of theophylline microcapsules.
abstract: The study was aimed to investigate microencapsulation of theophylline using different ratios of eudragit S 100 as wall material by the emulsion solvent evaporation technique.  The release profiles, effect of stirring speed and different pH of dissolution medium on release profiles and stability were also studied. Various formulations of microcapsules were compressed in to tablets. In vitro dissolution studies indicated that the rate of drug release was reduced with an increase in the amount of Eudragit S 100. Moreover, the release data of various formulations were fitted to Zero order, First order, Higuchi, Hixson Crowell and Korsmeyer Peppas kinetic models.  It was observed that the release of drug from all the formulations followed Higuchi's kinetic model as its value of coefficient of determination is greater than that of others. The release profiles of the test formulation in distilled water and various pH media were compared and decreased release rate was seen at lower pH i.e. pH 1.0. Slight or no change was apparent in the release rate at higher stirring speed compared to lower stirring speed. No significant changes were also observed in the drug release profiles of test tablets stored at different temperatures. Test tablet (F2) was found to produce similar and sustainable release rate compared to commercial product, Quibron-T/SR tablet on the basis of their T(70%). Similarly, f(2) values of reference versus F2 is 66.98 which show less difference between these two as compared to the comparison of reference with F1 and F3.
authors.affiliation: Faculty of Pharmacy and Alternative Medicines, The Islamia University of Bahawalpur, Bahawalpur, Pakistan. ma786_786@yahoo.com
authors.forename: Mahmood
authors.initials: M
authors.lastname: Ahmad
authors.forename: Naveed
authors.initials: N
authors.lastname: Akhtar
authors.forename: Ghulam
authors.initials: G
authors.lastname: Murtaza
authors.forename: Syed Wajid
authors.initials: SW
authors.lastname: Hussain
mesh_terms: D002214:Capsules / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003692:Delayed-Action Preparations / Q000737:chemistry; D004339:Drug Compounding / Q000379:methods; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015233:Models, Statistical; D010316:Particle Size; D011109:Polymethacrylic Acids / Q000737:chemistry; D012995:Solubility; D013607:Tablets / Q000737:chemistry; D013806:Theophylline / Q000737:chemistry*
chemical_list: D002214:Capsules; D003692:Delayed-Action Preparations; D011109:Polymethacrylic Acids; D013607:Tablets; C038300:methylmethacrylate-methacrylic acid copolymer; D013806:Theophylline