الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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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.