II. peak valley plasma concentration time profile is



The  oral  route 
of  drug  delivery system  is 
the  most  important 
method  of  administering 
drugs  for systemic effects. The parenteral
route is not common used for self administration of medication. The topical
route of administration has only recently been employed to deliver drugs to the
body for systemic effects. It is probable that at least 90 % of total drugs
used to produce systemic effects are 
administered  by  the 
oral  route.  When 
a  new  drug 
is  discovered,  one of 
the  first  questions 
a pharmaceutical  company going to
asks  is whether or not the drug can  be effectively  administered 
for  its intended effect by the
oral route. If it cannot, the drug is primarily relegated to administration in
a  hospital  setting 
or  physician’s  office. 
Solid  oral  dosage 
forms  represent  the 
preferred  class  of product. The reasons for

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this preference are well known.

Traditional drug delivery involves the formulation of the drug into a
suitable form, such as a compressed tablet for oral administration or a
solution for intravenous administration. These dosage forms have been found to
have serious limitations in terms of higher dosage required, lower
effectiveness, toxicity and adverse side effects. New drug delivery systems
have been developed or are being developed to overcome the limitation of the
conventional drug delivery systems to meet the need of the healthcare


Problems of Traditional Drug

An ideal dosage for drug therapy
of any disease is one which immediately attain the desired therapeutic
concentration of drug in plasma and maintains it’s constant for the entire
duration of treatment. This is possible through the administration of
conventional dosage forms in a particular dose and at particular frequency. The
frequency of administration or dose interval of any drugs depends on its half
life or mean residence time and its therapeutic index.

In most cases, dosing interval is
much shorter than the half life of the drug, resulting in number of limitations
associated with such a conventional dosage form which is

Poor patient
compliance; increased chances of missing the dose of a drug with short half
life for which frequent administration is necessary.

A character
peak valley plasma concentration time profile is obtained which makes
acquirement of steady state condition difficult.

The inevitable
fluctuation in the concentration may lead to under medication or over
medication as the C ss value fall or rise beyond the therapeutic range.

The fluctuating drug level may
lead to precipitation of adverse effect especially of a drug with

small therapeutic index whenever
over medication occurs. Despite the fast pace of research and early-stage
discovery, many drug candidates fail during preclinical evaluation due to poor
efficacy, limited bioavailability,and other challenges associated with
effective drug delivery. Small molecule drugs can suffer from low solubility,
poor stability, short circulation time, and non-specific toxicity limiting
their therapeutic efficacy. Biopharmaceuticals such as nucleic acids, peptides,
and proteins are often limited by poor stability and rapid clearance from the
body. These challenges, coupled with the complexity and diversity of new
pharmaceuticals, are fueling the evolution of novel drug delivery systems that
overcome bioavailability and delivery obstacles. However, despite the growing
importance of polymer drug delivery methodologies, the materials and methods of
drug delivery are not widely available to those outside the polymer synthesis