Sustained Release Capsule Dosage Form

Abstract: The aim of the present study is to formulate and evaluate Venlafaxine SR capsules. venlafaxine is a novel anti-depressant used widely for treatment of depression and generalised anxiety disorder, but it is having disadvantage of less biological half life of about 5 hrs due to extensive hepatic first pass metabolism. So in order to maintain the therapeutic concentration of venlafaxine for a prolonged period of time the SR capsules has been formulated. The present research work was directed towards the development of a sustained release dosage form of venlafaxine in the form of capsules to be taken once daily. In the present study polymers such as Ethyl cellulose (10, 20, 50 cps), Hydroxypropylmethylcellulosephthalate, were used as coating polymers which helps in providing sustained release. The dissolution studies of the dosage form was performed and analysed by UV- Spectrophotometer. Different evaluation parameters such as drug- excipient compatibility studies were done by X-ray diffraction, Differential Scanning Calorimetry and in-vitro drug release was performed. Different polymers are optimized on the basis of release pattern. The marketed formulation was evaluated for the in-vitro release studies and the optimized formulation is compared with the marketed product which is in the form of extended release pellets. 1. INTRODUCTION Sustained release dosage (J. A. Campbell, 1959) form can be defined as a specific type of programmed release medication which contains in one dosage form equivalent of several single doses of a drug which is released to the body over an extended period of time and there by produces a sustained clinical effect The goal in designing sustained or controlled delivery systems is to reduce the frequency of the dosing or to increase effectiveness of the drug by localization at the site of action, reducing the dose required or provide uniform drug delivery. So, sustain release dosage forms provide a better control of plasma drug levels, less dosage frequency, less side effect, increased efficacy and constant delivery. Venlafaxine (Aukunuru Jithan, 2007) is a unique novel antidepressant that differs structurally from other currently available antidepressants. Venlafaxine and its active metabolite o-desmethyl venlafaxine is having the action of selective serotonin (Thomson, Physicians’ desk reference, 2004) and nor epinephrine uptake inhibiton. it lacks the adverse anticholinergic, sedative and cardiovascular effects of tricyclic antidepressants. The half lives of venlafaxine and its active metabolite are about 5 and 11 hours respectively. It is one of the majorly prescribed drug in US market about 17 billion prescriptions. Venlafaxine is more hydrophilic in nature and is having the disadvantage of extensive hepatic first pass metabolism. So to overcome and to maintain sustained level of venlafaxine in plasma levels the sustained formulation is selected in the form of capsules that are to be taken once daily. The present research work was directed to develop SR capsule of venlafaxine HCL and to match the release profile with the innovators products i.e Effexor TM -XR. (venlafaxine HCl). The formulated capsules were evaluated for in-vitro release. The optimized formulation was evaluated for in-vitro release and compared with the marketed one. The marketed product is available as capsules containing venlafaxine hydrochloride equivalent to 75mg in the form of extended release pellets. The optimized formulation was subjected to stability studies.