ABSTRACT
Optimizing drug therapy to patients is one of the important topics on the minds of all health care personnel. Drug developers, prescribers, and pharmacists would like to give the best drug to the patients, delivered in the most optimal way, to be taken the least number of times per day with maximized efficacy and minimal side effects. In this regard, modified-release dosage forms have found extensive use in today’s pharmaceutical armamentarium. Due to technological developments in the pharmaceutical industry, advanced drug delivery systems are being developed to improve patient compliance (by needing to take the drug less frequently) and, in several cases, improved efficacy with reduced side effects. Modified-release dosage forms have thus become very popular in improving patient therapy. These dosage forms have sometimes also been developed to extend the patent life of the drug and drug product. The major goal in designing an extended release (ER) product should be that of optimizing therapeutic effects and safety of a drug, while at the same time improving patient convenience and compliance through extended dosage intervals. In this chapter, we will primarily focus on oral extended-release dosage forms, although the principles can be applied to nonoral extended-release products as well, e.g., transdermal systems. It is important to note that extended-release dosage forms are more complex than immediaterelease dosage forms. Generally one dosage unit of extended-release product contains multiples of doses contained in an immediate-release dosage unit. In addition, the release of the drug from the extended-release product is intentionally modified. Therefore, it becomes extremely important to understand the release characteristics of these products as well as to evaluate how stable the release is under altered conditions in vivo, e.g.,
different pH, presence of food, etc. Because of these complexities involved in extendedrelease products, it is necessary to understand the regulatory considerations in evaluating these drug products.
