Classification Of Controlled Release Delivery System

Controlled release delivery system is employed showing that the medicine release kinetics is predictable as well as reproducible from one unit to another whether or not release account follow zero order kinetics.

Classification of managed release delivery system:

It can be labeled on the basis of their release device and the preparation the following

Physical system :

Diffusion managed systems

Monolithic systems

Dissolved drugs

Dispersed drugs

Porous systems


Biodegradable system

Reservoir system

Constant activity

Non continuous activity

Unsteady state

Ion exchange resin system

Osmotically control system

Hydradynamically balanced system

Other physical systems

Chemical systems :

Immobilization of the drugs


Biological system :

Gene therapy

Polymer as a drug delivery carriers:

For managed release drug delivery, polymers are known as structural backbones.

Polymers has pursuing properties

They may be enlarged, non inflamed, poriferous, non porous, erodible, bio adhesive etc.

Polymers applied for the prep of the manipulated release medicine delivery must fulfil pursuing requirements


2) Physical and mechanical properties

3) Pharmacokinetic properties

1) Biocompatibility

Polymer found in the handled release medication delivery should be biocompatible. Damaging pollutants must withdrawn before they contained in controlled release medicine delivery. Chemicals which are used in polymerisation process must be chosen carefully to meet regulatory need. E. g additives, stabilizers, plasticizers and catalyst.

Physical and mechanised properties

Polymers should fulfil certain properties required for the handled release medication delivery system design. These properties include elasticity, compactibility, amount of resistance to tensile, swelling and shear stress as well as resistance to tiredness.

Pharmacokinetic properties

Polymer shouldn't chemically degraded. If chemical substance degradation of the polymer will there be, degradation by product must be non poisonous, non immunogenic and non carcinogenic.

Controlled release medication delivery

Controlled release medication delivery is defined as release of the medication in a predesigned manner.

The main behind the handled release delivery of drugs is to encourage restorative benefits at exactly the same time reducing toxic effects.

Controlled release medicine delivery is used to minimize unwanted fluctuation of drug levels.


There are four principal mechanism behind the discharge of drug from managed release delivery system are as follows



Swelling accompanied by diffusion

Active efflux


Diffusion can occurs on a macroscopic range through skin pores in these devices matrix at the same time on a molecular level by moving between matrix substances.

Diffusion can take as the medication moves from the polymer matrix into exterior surrounding.

As drug release boosts, diffusion rate decreases because in controlled release system drug has to travel longer distance and needs a large diffusion time to release.


Diffusion is thought as a process of mass copy of individual substances of the chemical as a result of random molecule action and associated with a driving a car make such as concentration gradient.

Diffusion is a very significant phenomenon in pharmaceutical technology.

e. g. diffusion of drug across a natural membrane needed for a medication to be ingested into and excreted from the body.

Drug release requires multistep includes multistep that include diffusion, disintegration, deaggregation and dissolution.

Diffusion is a comparatively poor process and as a result of random molecular motion.

Concentration gradient is the driving a vehicle force.

Fick laws and regulations of diffusion

Fick became aware that the numerical equation of heat conduction originated by fourier can applied to mass copy.

These fundamental associations suggest the diffusion process in pharmaceutical systems.

Amount M, of the materials passing through a unit mix section S, in a time interval t is recognized as flux J

J= dM/S. dt. . . . . . . . . . . . . . . . Ficks first legislations of diffusion equation.

Flux J is directly proportional to awareness gradients dc/dx

J = -D dc/dx

D = diffusion coefficient of your drug.

C = concentration (g/cm 2)

S = surface area (cm2)

t = time in seconds

J = g/cm2 second

Negative signal of the diffusion equation reveals the diffusion is apposite to increasing amount. Diffusion is occurs apposite compared to that of increasing focus.

D is known as diffusion coefficient and it is influenced by awareness, temperature, pressure, solvent properties and substance character of the diffusant.


Dissolution is the procedure by which a solid stage (tablet or capsule) gets into into a remedy period i. e. normal water.

Drug dissolution uses few steps

Initially solid debris are separated

Solid particles integrate with water.

Then they look like an integral part of liquid solution.

Drug dissolution is the procedure of which medication substances are released from a good phase and goes into solution phase.

2) Swelling accompanied by diffusion

Initially these system is dried out and when the system is located in body, absorbs water or other body liquid leads to swell.

Swelling increases the aqueous solvent capacity in the drug and polymer mesh size which contributes to diffusion of medicine through enlarged network into external surrounding e. g hydrogels

Hydrogel are able to absorb a significant amount of the liquid upto 60 to 90 % drinking water. Within the hydrogel bloating can be triggered by a change in environment encircling the delivery system. These factor includes shifts in pH, temps, ionic durability and other factor which lead to bloating or shrinking of the system. Swelling contributes to release of the medication at the same time shrinking brings about blockage to the medication release.

Biodegradable systems

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After the discharge of the active ingredient these systems degrade within the body therefore of natural natural process.

4) Dynamic efflux

Example: Elementary osmotic pump. It is also known as OROS.

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When these sytem located in the body, water goes by through the semi permeable membrane of the machine which causes expansion of the osmotic pump. Osmotic pump pushes medication outside via a delivery orifice into gastro intestinal tract. Drug release of the osmotic pump is managed by the structure of the membrane.

Advantage of the managed release medication delivery:

In managed release medicine delivery reduction in dosing frequency when compared with conventional medication delivery.

Reduction in fluctuating medication levels

It helps to increase patient compliance

It provide more even effect

It help to avoid nighttime dosing

It also assist in reduction in dose related side effects

It really helps to achieve more consistent pharmacological effect

Reduction in cost

It facilitate improvement in treatment efficiency

It assist to reduce local and organized side effects

It really helps to improve bioavailability of drugs

It also helpful in reduce lack of medicine activity.

It minimizes medicine accumulation

Disadvantage of the handled release medication delivery:

Controlled release drug delivery is expensive, unpredictable

It has poor in vivo "in vitro correlation

If drug goes through significant first move clearance, the drug bioavailability is reduced.

In managed release drug delivery, there may be risk of accumulation of the medicine in the body.

Some medicine has narrow healing index in cases like this we must maintain serum medicine level within thin range such drugs are difficult to create as controlled release medicine delivery.


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