DESIGN AND IN-VITRO EVALUATION OF SUSTAINED-RELEASE MATRIX TABLETS OF TIMOLOL MALEATE

  The aim of the present study was to prepare and characterize twice-daily sustained-release matrix tablets of Timolol maleate (TM) using different concentrations of hydrophilic Hydroxypropylmethylcellulose (HPMC K100M CR) alone and its combination with hydrophobic ethyl cellulose (EC). Formulations prepared by the wet granulation technique and were evaluated for the release of TM over a period of 12 hours using United States Pharmacopoeia (USP) type-II dissolution apparatus. Along with physical properties, the dynamics of water uptake and erosion degree of tablets were also studied. The in-vitro drug release study revealed that formulation F3 (40% wt/wt HPMC K100M) could extend the drug release up to 8 hours. The most successful formulation of the study, F5 (HPMC to EC, 1:1), extended the drug release up to 12 hours, exhibited satisfactory drug release in the initial hours, and the total release pattern was close to the theoretical release profile. The drug release from optimized formulation (F5) followed first-order kinetics via Non-Fickian (anomalous) diffusion. FTIR studies revealed that there was no interaction between the drug and excipients. In conclusion, the results indicated that the prepared sustained-release tablets of TM could perform therapeutically better than conventional tablets with improved efficacy and better patient compliance.   Key words: Timolol maleate; Matrix tablets; Sustained-release; Ethyl cellulose; Hydroxypropylmethylcellulose; In-vitro drug release.