Development of Sustained Release Matrix Tablets of Ramipril and Evaluation of Polymer Effect on In-vitro Release Pattern

The objective of the current study was to design an oral sustained release matrix tablet of Ramipril and to evaluate the effect of polymer on release pattern of the drug. Tablets were prepared by direct compression method using Methocel (Hydroxy Propyl Methyl Cellulose) K100MCR and Methocel (Hydroxy Propyl Methyl Cellulose) K4MCR, as matrix forming polymer. Dissolution studies were carried out in 500 ml phosphate buffer (pH 6.5) for 8 hours. The release mechanism was explored with zero order, first order, Higuchi equation and Korsmeyer's equation. The drug release followed Higuchi equation. It was found that the release of drug from matrix tablet decrease with the increasing of percentage of polymer. The two high viscosity polymers (Methocel K4MCR and Methocel K100MCR) were found suitable for the study. INTRODUCTION: Among all the developed and sophisticated solid drug delivery systems, tablets are the most convenient solid dosage form. All active pharmaceutical ingredients (APIs) do not have suitable physicochemical properties for tablet production, storage and administration. In this case coating may be used . It can be used to improve taste, appearance and to mask odor. Additionally, coating is used in tablet production for the purpose of protecting the APIdegradation in the stomach, and sustained-release coating is used to obtain favorable API absorption rate, and optimum plasma-release profile . Sustained release dosage forms are designed to achieve a prolonged therapeutic action by continuous releasing medication over an extended period of time after administration of single dose. In order to achieve steady level of medication, biodegradable polymer may play a vital role due to their biodegradability . One of the most favorable polymers is hydroxyl propyl methylcellulose (Methocel) which is prepared by the reaction of methylchloride and propylene oxide with alkali cellulose . Matrix system appears to be a very attractive approach from the economic as well as from the process development and scale up point of view in modified release system. Methocel is used frequently as a rate controlling polymer in matrix tablets. Methocel offers the advantage of being non toxic and relatively inexpensive; it can be compressed directly into matrix and is available in different chemical substitution, hydration rates and viscosity grades. When hydrophilic matrices interact with aqueous media (water, buffers, physiological fluids etc.) both the polymer hydration and the dissolving of soluble components take place. Dissolution of the drug at tablet surface cause a burst effect in the release profile of the system. This is more or less pronounced depending on the drug solubility and the polymer hydration rate 7, . The release kinetics working after the initial which inurn depends on the relative position of the eroding front and the swelling front.