Novel strategies and novel dosage forms which are far

Novel GIT Drug Delivery
System (NDDS) alludes to the methods, formulations, apparatuses, and techniques
for delivering a pharmaceutical compound in the body as basic for accomplish
its reasonable remedial impacts precisely and with safety . NDDS is a blend of
advanced strategies and novel dosage forms which are far predominant than
conventional dosage forms.

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  As the foremost purpose of
every dosage form is to reach patient in an efficient manner with efficacy and
safety so that it can give the required therapeutic results.

·        
To hampered dosage form the git environment to safe the
medicament from the degradation

·        
To  prevent injurious side-effects

·        
To enhance drug bioavailability

·        
Targeted drug delivery

·        
To increase patient compliance

·        
Possible treatments for in advance incurable
diseases

·        
Suitable for prophylactic benefits

·        
Better ease

Novel GIT drug delivery
systems:

1.     
Oral Osmotic DDS

2.     
Ion exchange controlled DDS

3.     
pH controlled DDS

4.     
Bio/muco-adhesives DDS

5.     
Floating DDS

1. Oral Osmotic DDS:

    Introduction:

Oral
medication therapy is the best favored and suitable choice as the oral route
offers quick dynamic surface region from other medication conveyance framework
for organization of a few medications. In regular oral medication route, there
are no such points of confinement to have such available control over arrival
of the medication and compelling fixation at the diseased site. It was
accomplished by unpredictable dosage regimen. This kind of dosing design result
is variety in remedial plasma fixations, that outcomes in serious reactions Furthermore, the
level of retention of medication from routine measurement structures may
contrasts subjected upon reasons, for example, expansion of excipients,
physicochemical parts of the medication, a few physiological factors, for
example, nearness or nonattendance of food, pH of gastro intestinal tract,
gastro intestinal motility. Sudden arrival of medication without having control
may prompt neighborhood gastro intestinal or fundamental toxic effects. In this
manner, a few strategies are made, which will overcome the deficiencies of
traditional measurements, which involves managed/controlled medication
conveyance framework. There are three principle classes of controlled-discharge
medicate conveyance basis; transdermal, intravenous, other than oral
frameworks.

Alza Corporation R of
USA was the first to develop an oral osmotic pump.

Advantages:

Osmotic drug delivery system for oral and parenteral consumption offer different and useful advantages
over other routes of delivery. The following
advantages provided to the approval
of osmotic drug delivery systems.

·        
They
afford a zero order release profile after an early lag.
·        

·        
Deliveries
may be late or pulsed if preferred.
·        

·        
 Drug release is free of
gastric pH and hydrodynamic condition.
·        

·        
They
are well characterized and understandable.
·        

·        
The
release mechanisms don’t depend on drug.
·        

·        
An
elevation of in-vitro and in-vivo correlation
(ivivc) is attained in osmotic systems.
·        

·        
The
reasonable for this approach is that the existence of water in
GIT is persistent, in terms of the
capacity required for stimulation and regulatory osmotically
base tools. ·        

·        
Greater discharge
rates are achievable with osmotic
systems compared with previously diffusion-controlled drug
delivery systems.          

·        
The
discharge from osmotic systems is somewhat affected by the
presence of food in gastrointestinal tract.
·         

·        
The
release ratio of osmotic systems
is precisely achieved and can be automated by
modifying the release control parameters

Disadvantages:

·        
Expensive
·

·        
If
the coating process is not exact there is a threat
of film defects, which results in dose dumping.     

·        
Size
hole is important ·        

·        
Chances
of Dose wastage ·        

·        
Recovery
therapy is not possible in the case of unpredicted adverse events.

Principle and basic concept of osmotic drug
delivery system:

It is established on the trust of osmotic pressure.
Osmotic pressure remnants a colligative stuff,
which depend on on amount of solute that is vital influence
of this phenomenon. Solutions of variable amount having the similar
solvent and solute system demonstrates

That osmotic pressure is proportional to their
concentrations. Thus a constant osmotic pressure, and thereby a
continuous influx of water can be acquired by an
osmotic drug delivery system. Osmotic pressure is related to
temperature and concentration and
the relationship can be described by following equation.

 ? = n2 RT 

Where, ? = osmotic coefficient 

n2 = molar concentration of solute in the solution

R = gas constant 

T = Absolute temperature 

 Basic formulation concept:

 Osmotic drug delivery devices
includes of an osmotically active drug
core, which is confined by a rate controlling semipermeable membrane.
Osmotic drug delivery system contrasts from diffusion based
systems in that the delivery technique of the active
agents is compelled by an osmotic
gradient rather than the concentration of drug in
the device. In the convenient and stress-free type of
osmosis-controlled drug release the following sequence of
steps are included in the release process:

1.      Osmotic transport of liquid
into release unit.

2.      Dissolution of drug into
the release unit.

3.      Transport of a
saturated drug solution by passing of the solution
through a single hole via orifice  in the semi permeable.

4.      The transport of active
agent from oral osmotic systems is maintained by the

5.      Invasion of solvent
via semi-permeable membrane, which in turn transports the
active agent to the external environment.

 Basic component of osmotic DDS:

§  Drug : functioned
as a osmogen else osmogenic salt is added in formulation’

§  Semi-permeable membrane :

§  Criteria

1.     
Sufficiently wet power and water
permeability.

2.     
Should be compatible biologically and
inflexible.

3.     
Should be adequately thick to repel the
pressure of device.

4.     
Any polymer that is capable of
absorbing water but impermeable to solute can be used as a coat substance
.e.g.; ethyl cellulose, Cellulose acetate, cellulose triacetate.

§  Hydrophilic and hydrophilic
polymers :  CMC,
HPMC , HEC

§  Wicking agent : SLS ,
PYP , Bentonite

§  Solubilizing agent : PVP
,CP , PEG

§  Osmogens : Nacl , KCl

§  Plasticizer : Phathaltes , benzoates , TEC

§  Flux regulator : Polypropylene , polybutylene

§  Pore forming agent : Calcium nitrate , Potassium sulphate

§  Coating solvent : acetone and methanol (80:20) , acetone and water
(90:10)

§  Surfactants : poly oxyethylenated castor oil

Methods to create a delivery orifice in the
osmotic tablet coating are:

Mechanical drill

Laser drill: This
development is well established for creating sub-millimeter size orifice in
tablets. Usually, CO2 laser beam (with output wavelength of 10.6?) is utilized
for drilling e, which gives excellent reliability features at minimum costs. It is
likely to regulate the size of the passageway by changing the laser power,
firing period (pulse time), thickness of the wall, and the dimensions of the
beam at the wall.

 

·        
Indentation that is
not covered while coating process: This is made in core tablets by employing
better punches that have needle on upper punch and is not covered while  coating process which behave as a path for
drug release in osmotic system.

·        
Utilizing  leachable materials in the semi permeable
coating: e.g. controlled porosity osmotic pump

Factors
that affect the drug release from osmotic delivery of drugs:

:
                           The drug
delivery from osmotic delivery device rely on various process and
formulation aspects. Apart from the water miscibility of the drug,
the solubility of the further fundamental ingredients can also have main impact on
the drug delivery by producing an osmotic pressure gradient crosswise
the polymeric layer on interaction with dissolution medium. The rate of
drug release from osmotic pumps relies on the total solubility and
the osmotic pressure of the drug. Many features that influence the
release of drug from osmotic system are follows:

 Orifice Size: 

              
Osmotic drug delivery apparatus comprises of at least one
delivery orifice in the semipermeable membrane for drug delivery and the
diameter of delivery orifice  
should be optimized in order to regulate the drug release from
osmotic systems. To obtain an suitable zero-order delivery profile, the
area of the orifice should be reduced than a size Smax to
minimum drug delivery by diffusion through orifice. Moreover, the
area must be adequately large, above a minimum size Smin, to lessen
the hydrostatic pressure build up in the device. Else, the
hydrostatic pressure can break the membrane
and influences the zero-order release rate of drug.
Therefore, the cross sectional area of the orifice must be maintained
between minimum and maximum values.

 Solubility:

           
The delivery rates of drug rely on the solubility of
the solute inside the drug delivery device. Subsequently,
drugs should have adequate solubility to be delivered by osmotic
delivery on the other hand, most water-soluble drugs
would revealed high delivery rate that would be zero-order for a
small percentage of the initial drug load. In the case of low
solubility compounds, various other approaches may be applied and can be
divided into two categories. First, swell- able polymers can be
added that gives in the delivery of poorly soluble drugs in the
form of a suspension. Second, the drug solubility can be altered
by using different techniques.

Semi permeable Membrane:

                 The selection of a
rate-controlling membrane is a significant characteristic in the formulation
design of osmotic systems. Drug release from osmotic systems is
not influenced by pH and agitational force of the
gastrointestinal tract to a greater 
degree because of the reason that selectively water permeable
membrane and operative isolation of dissolution from the gut environment.
The thickness of membrane is kept between 200 and 300 mm

Use
of encapsulated excipients:

               A capsule device layered
with uneven membranes to transport drugs with
poor water-solubility .For instance, solubility of a poorly
water-soluble drug such as glipizide was increased by using
bicarbonate, it was employed as encapsulated
excipients (pH-controlling excipients) in the capsule
device. The solubility modifier (meglumine), in the form of
mini-tablets, was coated with a rate controlling membrane to delay
its availability inside the core. Thus, the solubility
of glipizide was improved to its delayed release from the device.
  

 

 

 

 

 

 

·       
Use of cyclodextrin derivatives:

 These enhances  the drug solubility and dissolution
through addition of complexation or solid dispersion which
behave as hydrophilic carriers for drug with inadequate