Abstract: Matrix system are favoured because of their simplicity, patient compliance etc, than traditional drug delivery(TDS) which have many drawbacks like repeated administration, fluctuation in blood concentration level etc. Developing oral sustained release matrix tablets for highly water-soluble drugs with constant release rate has always been a challenge to the pharmaceutical technologist. Most of highly water-soluble drugs, if not formulated properly, may readily release the drug at a faster rate, and are likely to produce toxic concentration of the drug on oral administration . Hydrophillic polymers have become product of choice as an important ingredient for formulating sustained release formulations of highly water soluble drugs. Drug release through matrix system is determined by water penetration, polymer swelling, drug dissolution, drug diffusion and matrix erosion. Highly water soluble drugs like metoprolol tartarate, ditiazem, tramodol, ranitidine has been formulated as sustained release matrix tablets.
Introduction: Traditional delivery systems (TDS) are characterised by immediate and uncontrolled drug release kinetics. Accordingly, drug absorption is essentially controlled by the body's ability to assimilate the therapeutic molecule and thus, drug concentration in different body tissues such as the blood, typically undergoes an abrupt increase followed by a similar decrease. As a consequence, it may happen that drug concentration dangerously approaches the toxic threshold to subsequently fall down below the effective therapeutic level. Unfortunately, also the strategy of repeated administrations does not completely prevent the above-mentioned drawbacks of TDS. On the contrary, the purpose of controlled release systems (CRS) is to maintain drug concentration in the blood or in target tissues at a desired value as long as possible. In other words, they are able to exert a control on the drug release rate and duration. Matrix technologies have often proven popular among the oral controlled drug delivery technologies because of their simplicity, ease in manufacturing, high level of reproducibility, stability of the raw materials and dosage form, and ease of scale-up and process validation. Oral drug delivery continues to rise in popularity as formulation scientists look for ways to control drug release and improve patient convenience. Oral drug delivery continues to rise in popularity as formulation scientists look for ways to control drug release and improve patient convenience. However, developing oral controlled release tablets for water-soluble drugs with constant release rate has always been a challenge to the pharmaceutical technologist. Most of these water-soluble drugs, if not formulated properly, may readily release the drug at a faster rate and produce a toxic concentration of the drug on oral administration. In recent years, considerable attention has been focused on hydrophilic polymers in the design of oral controlled drug delivery systems because of their flexibility to obtain a desirable drug release profile, cost-effectiveness, and broad regulatory acceptance. Among the hydrophilic polymers, cellulose derivatives such as methyl cellulose, hydroxypropyl methylcellulose, and sodium carboxymethyl cellulose are generally considered to be stable and safe as release retardant excipients in the development of oral controlled release dosage forms. Though various formulation approaches are used to control the release of water soluble drugs, multilayer matrix tablets are proving to be potential. In this review we have focused on the formulation of highly water soluble drugs, which will be a useful source of information to the people working in this field.
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