Design and Pharmacodynamic Evaluation of Optimized Microporous Osmotic Tablets of Venlafaxine Hydrochloride

Osmotically controlled oral drug delivery systems utilize osmotic pressure for controlled delivery of active agents[3]. These systems can be utilized for systemic as well as targeted delivery of drugs. The release of drugs from osmotic system is governed by various formulation factors such as the solubility and the osmotic pressure of the core components, nature of the rate controlling membrane[4]. Drugs can be delivered in a controlled pattern over a long period of time by the process of osmosis. Osmotic devices like Rose-Nelson pump, Higuchi-Theeuwes pump and elementary osmotic pump are the most promising systems for controlled drug delivery[5,6]. Osmotic technology has been investigated to obtain controlled release profile for drugs such as theophylline, salbutamol sulphate[7], metoprolol tartrate[8] and diltiazem hydrochloride[9]. Swellable elementary osmotic pump was developed to achieve zero-order release for nifedipine, which is poorly water-soluble[10]. Park et al.[11] developed a novel squeeze-type osmotic tablet for nifedipine composed of one or more polymeric ring type of squeeze-push layer (squeeze-disc) and a centered drug core. An assymetric membrane system was developed for felodipine and nifedipine to improve the osmotic effect and achieve controlled release of the model drugs[12]. Design and Pharmacodynamic Evaluation of Optimized Microporous Osmotic Tablets of Venlafaxine Hydrochloride