The class of product. The reasons for this

The  oral 
route  of  drug 
administration  is  the 
most  important  method 
of  administering  drugs 
for systemic effects. The parenteral route is not routinely 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 all 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 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

this preference are well
known.

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Problems of
Traditional Drug Delivery

An ideal dosage regimen in
the 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 upon 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 are

1.     
Poor patient compliance; increased chances of missing
the dose of a drug with short half life for which frequent administration is
necessary.

2.      A typical peak
valley plasma concentration time profile is obtained which makes attainment of
steady state condition difficult.

3.     
The unavoidable 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.

 

Need for New
Approach of Drug Delivery System

To overcome the problem that
we mention before, it clearly indicates that the need of the development of the
non traditional dosage forms.

There are 2 ways to overcome
such situation

1.     
Development of new, better and safer drugs with long
half life and large therapeutic indices.

2.     
Effective and safer use of existing drugs through
concepts and techniques of sustained/ controlled and targeted drug delivery
systems.

Oral controlled/sustained
release dosage forms are being developed since past three decades due to their
advantages. The design of oral controlled/sustained release drug delivery
systems should primarily be aimed at achieving more predictable and increased
bioavailability of drugs.

 

III. NEW
APPROACHES OF DRUG DELIVERY SYSTEM

 

The oral form of drug
delivery system is considered the most preferred an patient convenient means of
drug administration. While significant advances have been made in the
development of elegant systems to modify the oral delivery of drugs, the basic
approaches have remained

unchanged. Modified release
formulation technologies offer an effective means to optimize the bioavailability
and resulting blood concentration time profile of drugs. Modified release

dosage forms are those
preparations where the rate and/ or place of release of the active substance(s)
are different from that of a conventional release dosage form administered by
the

same route. This deliberate
modification is achieved by a special formulation design and/ or

manufacturing method.

 

Examples of New Approach of
Drug Delivery System

1.     
Printing Of Small Molecular Medicines From The Vapor
Phase

The growing need to develop efficient methods for
early stage drug discovery, continuous manufacturing of drug delivery vehicles,
and ultra-precise dosing of high potency drugs. The
manufacturer of film form medicine like the dispersion of API particles in a
matrix of polymer by doing the mixing, spraying, dipping and folloed by
extrusion or casting (18). The approaches were suffer from limited dispersion
of particle, stability, and loading of drug, in particular if working with
nanoparticles(14). To overcome the problem above, we using a process which
originally developed to achieve the continuity, free of solvent, big scale,
high-troughput, yet ultra-precise printing of small-molecular organic
semiconductor or what we called as organic vapor jet printing (OVJP) (22) as
the results we got the small pharmaceutical ingredients molecular which is have
the nanocrystalline morphology. The printed films show dissolution kinetics
substantially enhanced compared with it’s powder form.

2.      Mesoporous silica nanoparticles as
controlled release drug delivery and gene transfection carriers

At some
cases, for example the chemotheraphy for cancer, the current treatment method
mainly rely on the use of cytotoxic drugs that only have limited effectiveness
and adverse side effect. Many studies have indicated these problems could be
caused by the lack of target specificity in the formula of antitumor drugs. To
overcome this problems a pursuit to design a target specific drug delivery
system that can transport an effective dosage of drug molecules to targeted
tissues and cells is the answer. At first, it looks nearly impossible to found
the material that have high fondness for adsorbing certain drug molecules, yet
willingly to release the same compound upon reaching the designated tissues or
cells. Recently some of “smart” drug delivery system which is biodegradable
compounds such as  liposomes, dendrimers,
and polymeric nanoparticles that can control the release of pharmaceutical
drugs solution of water upon the degradation of the carrier trigerred by
various factor for example the pH or under physiological conditions. While some
drug delivery system have been following this approach, it is still a challenge
to eliminate the premature release of drug in these structurally unstable
compounds. In another hands some good progress shown promise on the uses of
mesoporous silica nanoparticles as intracellular controlled release drug
delivery agents. The mechanism which transformed non-functionalized MSN into stimuli-responsive
drug delivery agents have been established, although further improvements are
expected in terms of increasing the inventory of gatekeepers and controlled
release mechanisms. With this great potential, in the future application it is
possible that some functionalized MSN perform specific tasks inside of
cells.(2)

3.      Gold nanoparticles in delivery
applications

Gold nanoparticles (GNPs) have recently emerged as an
attractive candidate as an drug delivery agents because it provide non-toxic
carriers for drug and gene delivery application. The other advantage is their
ease of synthesis, the monodisperse of gold nanoparticles can be formed with
core sizes ranging from 1 nm to 150 nm and also the photophysical properties
could trigger drug release at certain places.

Figure 1. Various application of gold nanoparticles in
theraphy

In biomolecules, GNPs have shown the success as drug
delivery materials for DNA/RNA, peptides and proteins. It is been known that
viruses could provide a vehicle for gene theraphy and had been shown highly
efficient. (52) The effective delivery vehicles need to provide efficient
protection of nucleic acid from degradation by nucleases, efficient cell entry,
and release of the nucleic acid in functional form in the nucleus (55). GNPs
can be made a small particle to provide a high surface to volume ratio,
maximizing the carrier ratio. There is also a photothermal effect of gold
nanoparticles in theraphy. El Sayed et al. have recently reported about
potential use of GNPs in photothermal destruction of tumors (68).
Citrate-stabilized GNPs (core d=30 nm) were coated with anti-EGFR (epidermal
growth factor receptor) to target HSC3 cancer cells (human oral squamous cell
carcinoma). The use of GNPs enhanced the efficacy of photothermal therapy by 20
times. The GNPs have been showing its promising results as an drug delivery
agents. Mostly because of it’s combination of low inherent toxicity, high
surface area and tunable stability provides them with unique attributes that
should enable new delivery strategies.