Formulation of controlled porosity osmotic pump tablets containing venlafaxine hydrochloride

Venlafaxine hydrochloride is an antidepressant agents, it has a short biological half-life (5 h) thereby requiring twice a day dosing to maintain adequate plasma levels of drug. The aim of this study was to formulate Controlled porosity osmotic pump (CPOP) tablets containing venlafaxine hydrochloride to be taken once daily. In this study, the core tablets consist of microcrystalline cellulose pH 101 and osmogents (sodium chloride, mannitol, lactose) were prepared by wet granulation method. The core tablets were coated semipermeable membrane of cellulose acetate containing polyethylene glycol 400 as a pore former and plasticizer, Tween 80 as a surfactant. The coating operation was performed using a pan coating machine. The formulation variables affecting on drug release in vitro, coating weight, concentration of pore former and surfactant were investigated using D-optimal design. The optimal tablet formulation has been proposed. An invention product, efexor® XR extended release capsules was used as reference for study in vitro. It was found that drug release rate was inversely proportional to coating weight and directly proportional to the concentration of pore former and surfactant in membrane. The drug release profile from the optimized formulation was similar to that from reference drug. CPOP tablets of venlafaxine hydrochloride were successfully prepared, the drug release from the tablets was extended for 24 hours. The CPOP tablets were prepared by coating the core tablets with a pore forming agent which is likely to be most cost-effective than laser drilling.