Development and evaluation of gastroretentive floating tablets of an antidepressant drug by thermoplastic granulation technique

The present study was undertaken with an aim to formulate, develop and evaluate gastroretentive floating tablets of an antidepressant drug, Venlafaxine HCl (hydrochloride), which release the drug in a sustained manner over a period of 24 h. Three different hydrophobic retardants namely hydrogenated cottonseed oil, carnauba wax, cetyl alcohol and a hydrophilic polymer Methocel® (hydroxy propyl methyl cellulose (HPMC)) K15M were used in different combinations at different ratios for the preparation of tablets. The tablets were prepared by Hot Melt or Thermoplastic granulation method and evaluated for tablet thickness, hardness, weight variation, friability, floating lag time and in vitro drug release. Formulation F8 with hydrophilic polymer (Methocel® K15M) and hydrophobic retardant (carnauba wax) in the ratio 1:2.6 (approx.) was considered as an optimized formulation. The optimized formulation showed satisfactory sustained drug release and remained buoyant on the surface of the medium for more than 24 h and its release profile was comparable with the marketed formulation (VENTAB-XL 37.5). It can also be concluded that floating drug delivery system of Venlafaxine HCl can be successfully formulated as an approach to increase gastric residence time and thereby improving its bioavailability.