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Abstract Conventional dosage forms do not provide rate-controlled release or target specificity. In many cases, conventional drug delivery provides sharp increases of drug concentration at potentially toxic levels. Following a relatively short period at the therapeutic level, drug concentration eventually drops off until re-administration. During the past three decades, however, ”controlled drug delivery systems” have been widely developed and provide an attractive alternative for modified delivery of therapeutic agents. Such dosage forms offer great advantages over conventional therapy including minimized in vivo fluctuation of drug concentrations and maintenance of drug concentrations within a desired range, drug delivery to target sites in a predetermined fashion, drug protection from a hostile biological environment, suppression of the drug adverse effects, and reduction of the drug dose and the frequency of administration. This would contribute to the optimization of drug therapy leading eventually to improved patient adherence and greater therapeutic outcomes.[1, 2] The current methods of drug delivery exhibit specific problems that scientists are attempting to address. For instance, injectable medications could be made less expensively and administered more easily if they could simply be dosed orally. However, this cannot happen until methods are developed to safely shepherd drugs through specific areas of the body, such as the stomach, where low pH can destroy a medication, or through an area where healthy bone and tissue might be adversely affected.[2] These goals can be achieved using carrier-mediated drug delivery systems. 1. Carrier-mediated drug delivery Carrier-mediated drug delivery has emerged as a powerful methodology for the treatment of various pathologies. Carrier-mediated drug delivery could enhance therapeutic efficacy via increasing the specificity reaching in some cases to a cellular level specificity, controlling release kinetics, protecting the active agent or a combination of these mechanisms.[3] A successful drug carrier system needs to demonstrate optimal drug loading and release properties, long shelf-life and low toxicity.[4] Numerous carrier systems have been developed for the controlled delivery of biologically active molecules including drugs (Figure 1). Some of these pharmaceutical drug carriers are defined below. |