Hi bloggers.

Here comes my blog regarding the gastro retentive drug delivery system.

In this blog I will cover the introduction, method of preparation and systems involved in the development of GRDDS.

The dosage forms that have the capability to remain in the stomach are termed as gastro retentive drug delivery systems or floating drug delivery systems. (1)

These drug delivery systems are useful in the case of the drugs like (1)

-antacids (here we need a local action)

-drugs like verapamil, diazepam, chlordiazepoxide etc which are not soluble to good extent at more pH values.

-for drugs whose absorption is fast in stomach

-drugs which may undergo degradation in colon

-drugs which are unstable at the intestinal conditions

So let's go through the gastric emptying, which is key for these delivery systems briefly. Gastric emptying takes places when ever we take the food or even the person is in fasting state.

In the fasting state, there will the generation of the migrating myoelectric cycle that is divided in to 4 phase, say Phase I Phase II Phase III and Phase IV.

In Phase I the contraction occurs after long intervals.

In Phase II an intermediate level of the contractions and action potential takes place.

In Phase III intense contractions occur at a faster rate.

Phase IV is the time difference between Phase III and Phase I of the next cycle.

During the feeding stage the shift from the fasting to the feeding takes place. Here it's called digestive motility pattern and it resembles the phase II of the fasting stage. (2)

Some facts regarding gastric retention: (2)

i.Gastric emptying is mainly based on the volume, viscosity and calorific value of the food we take.

ii.the fluids which are having the same temperature as of the body will have more gastric emptying rate than the fluids that either cold or hot than our body temperature.

iii.the particles which have the diameter of 7.5mm will have longer gastric retention time than the particles having the size of 9.9mm.

iv. The substance which are less dense than the gastric fluids retain for the longer period of time.

Now let's come to the preparation.

Method(s)of Preparation:

1. Single unit dosage form: Here the drug and the hydrocolloid are randomized. Gas evolving substance may or may not be added. Whenever the selling of the hydrocolloid occurs then the drug will be liberated out. (1)

2.Multiple dosage form: here the microspheres are used. The microspheres are made up of the substances like albumin, gelatin, polymethylacrylate and polyacrylamine. (1)

In this forms the sustained release forms are coated with the effervescent material which is further coated with the swellable substances. These swellable substances are made of materials like polyvinyl acetate and purified shellac. (3)

3. Intragastric floating drug delivery systems: Here a microporous compartment having pores on the upper and bottom side will enclose the drug reservoir. (1)

4. Intragastric inflatable Drug Delivery system: It is also called osmotic controlled drug delivery system which consists of a capsule that has a osmotic pressure controlled drug delivery device and floating support. Whenever the system reaches the stomach then there will erosion of the capsule so that the osmotic controlled device is released out. (1)

There are two systems used in the development of GRDDS. They are effervescent and non-effervescent systems.

Let's go through them.

Effervescent systems: in this system there is a matrix which is made up of polysaccharides and effervescent substances like sodium bicarbonate, citric acid etc. whenever the system reaches the stomach there will be the release of the carbondioxide because of the acid environment. The gas released gets entrapped in the matrix layer and it results in maintaining buoyancy. The addition of the carbonates also gives the alkaline environment that helps in the conversion of the polymer to gel. (1)

Noneffervescent systems: Here in this drug delivery system there will be a gel forming or substances that can swell excessively, polymers that can form matrix like polycarbonates and polyacrylates are used. (1)

The process includes simple the randomization of the drug and hydrocolloid. In the stomach there will be swelling and therefore the density will become less than 1 and hence then buoyancy is maintained. (2)

In the next blog I will present the evaluation, commercially available drugs advantages, and disadvantages.

Reference:

1.Indian Drugs, Scientific and research publication from Indian Drug Manufactures Association, volume 48, issue no 05, may 2011, page no 7 to 11.

2. http://www.aapspharmscitech.org/articles/pt0603/pt060347/pt060347.pdf (accessed on 20th August 2011, 20:30)

3. http://rjptonline.org/RJPT_%20Vol1(4)/8.pdf (accessed on 20th August 2011, 20:45)

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