Abstract

Microporous osmotic tablets were developed using controlled porosity membrane, which delivers drug in a controlled manner for prolonged period of time. The objective of the present investigation was to formulate and evaluate an oral osmotic drug delivery system for the antidepressant drug venlafaxine hydrochloride to achieve zero order release. Venlafaxine hydrochloride was selected as it has a short biological half-life and high aqueous solubility. Drug-excipient compatibility was studied using Fourier transform infrared spectroscopy. Core tablets were prepared by wet granulation method followed by coating. Sodium chloride and potassium chloride (1:1) were used as osmotic agents in the core tablet and polymers Eudragit RLPO and RSPO (1:1) were used for coating along with sorbitol (70% w/w) as pore formers. The tablets showed desired sustained release profile for 24 h. Optimization studies were performed to study the effect of concentration of osmotic agent and pore former on drug release (t_50% and t_90%). From in vitro release studies, it was evident that drug release was independent of dissolution media, agitation intensity, but highly dependent on the concentration of pore forming agents, osmotic agent and weight gain of the tablet coating. Scanning electron microscopy confirmed the microporous structure of optimized batch. The optimized formulation gave desired once a day release of venlafaxine hydrochloride without using laser drilling technique which would make it more patient compliant and cost effective.