for up pressure in the osmotic system and finally

for drug with high dose, with mixture of a drug/cyclodextrin Complex is
problematic, eg, paracetamol. The same phenomenon can also be
employed  for the osmotic systems 
·         Use of Swell-able polymers:
Polyethylene oxide, vinyl acetatecopolymer have even swelling rate which causes drug release at constant rate.
Also, the pressure build up while swelling does
not rupture the system 
·         Use of wicking agents: These
agents may improve the surface area of drug along with  aqueous fluids. E.g.Sodium lauryl sulfate and colloidal silicon dioxide, etc. Ensotrol® technology works on the same principle for drug
administration via osmotic system.
·         Use of effervescent mixture: It can be new tactic to deliver poorly water-soluble drugs
from osmotic delivery systems. After administration, the effervescent mixture having drug is deliveredunder pressure via 
delivery hole in the membrane 
Effervescent mixture of citric acid and sodium bicarbonate produces carbon
di-oxide which build up pressure in the osmotic system and finally  release the  drug at steady rate 
·         Co-compression of drug with excipients:  Different excipients can be
used to alter the solubility of drugs with mechanisms like
saturation solubility, pH dependent
solubility. For instance, such excipients are organic acids, buffering agent, etc. ·         Use
of alternative salt form: Change in salt form of drug may improve  solubility. It is observed that the salt of drug is too soluble to maintain a saturated solution and thus zero order release for the estimated delivery life of
dosage form. Afterwards osmotic pump is designed with this salt form that give extended
release up to 24 h.
·         Resin Modulation approach:
Ion-exchange resin methods are frequently used to alter the solubility of
drugs.Some of the resins used in osmotic systems are Poly (4-vinyl pyridine), Pentaerythritol, citric and adipic acids.

 

Classification of Osmotic
DDS Osmotic Drug
Delivery Devices fall in two categories:  
·         Implantable:
1       Implantable osmotic pump
2       Oral osmotic Pump      
      1.Implantable osmotic pump       2 Oral osmotic pump A )Single chamber osmotic pump:  B).Multi chamber osmotic pump   C) Modified osmotic pump   1. Oral osmotic pump A. the Rose
and Nelson pump: Origin:   This drug delivery system was initially  designed by the Australian scientists Rose and Nelson, in
1955 when they were administering drug to  the sheep and cattle gut Components            This drug delivery system
 contains three chambers               
1 .Drug chamber 2.    
Salt chamber holding salt bridge 3.    
Water chamber 4. Semi permeable membrane Working
       Semipermeable divides the
salt and water compartment
 as the water enters from water to
salt chamber due to gradient build up by osmotic pressure the salt chamber extends and forces
the drug chamber . Drug coms out of the orifice
and finally pumped from the DDS to the diseased  area. B. Higuchi Leeper osmotic pump
              This DDS is the advancement of Rose and Nelson pump, in its
design in a way that it
has no water
chamber. Components 1       Salt
chamber 2      
Drug chamber3       Semi permeable membrane 4       A rigid
housing Working     As is has no water chamber so through
the  of imbibition method  drug enters the
system and activates it .On implantation of
device the biological
liquid present in the environment  enters the salt chamber which
comprises of  the
fluid solution
, on enteringbiological fluid absorbs MgSO4 and build up a
osmotic pressure that in turn forces the movable partition towards drug chamber and drug comes
out of the
orifice Modification Through this system
pulsatile delivery
is accomplished . Pressure is the critical factor
.This is done by drilling the orifice
with stretching elastic material upto the specific concentration
pressure build up open the orifice and drug is delivered
one more time  after drug release pressure reduces and orifice get
closed. Application: This system is employed 

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