1.Enteric pharmaceutical capsules: Drastic change has been observed from organic solvent based system to the aqueous system from the past two decades. Usage of aqueous coating system has been considered as advantageous as it is eco friendly, which avoids environmental pollution. The main drawback with the aqueous system is that it is very much sensitive in hard gelatine capsule coating as it leads to shell embrittlement and poor adhesion of the coating material to the surface of the gelatine capsule. In order to overcome this draw back water soluble materials like hydroxypropyl methyl cellulose has been widely used for the coating purpose in the pharmaceutical solid dosage forms other than water soluble coating material water insoluble coating materials like acrylic resins, a vinyl polymer are used. If the active ingredient is water sensitive then the aqueous coating systems cannot be used. Usage of water in the place of solvent can reduce the cost. Using coating solution or dispersion of higher concentration shorten the coating time but the viscosity of the solution might be the problem.

Several novel approaches were developed to overcome the problems like increasing the effect of the operational conditions in capsule mass, the growth of kinetics on efficiency of coating. Disintegration tests to know the gastric resistant properties of the enteric coated products. In order to know the mechanical strength of the capsule traction X deformation tests are done. Mass distribution of the coating material is known by weighing. The structure of coating layer is analysed by scanning electron microscope. New coating technique like coating soft gelatine capsule by spouted bed (), enteric coating using cellulose derivative(), production of enteric capsules by hot melt extrusion(). These systems were equipped with several advantages at the same time accompanied with few disadvantages as well. So, this kind of technologies narrowed its applications. In order to know the performance of the coating in the intestine several technologies have been opted. Out of which Gamma Scintigraphy is an elegant technology()

In the current developing technology coating the capsules itself is an extra process which in turn results in increase in the coast, time and also labour. In order to avoid this it is preferable to include the materials containing eneteric properties in the formulation itself. Hence , no use of enteric coating where it saves the time and money as well.(ing 13)

A simple capsule is a hard shell capsule optionally containing medicament body and cap are joined one within another like the tubes of a jointed telescope and are thus capable of being extended or shortened. Enteric capsules are the capsules having enteric properties which mean possessing the properties like being soluble or easily disintegrated in alkaline secretions but not soluble or disintegrated in acid secretions of stomach. (oka)

advantages and disadvantages of enteric capules:

advantages:

enteric coating controls the location of the drug absorption in the digestive system.

As the word enteric relates to the small intestine, its purpose is to prevent the mediation from dissolving before it reaches the small intestine.

The enteric coating is seen as a thin shiny layer on the medicines.

Enteric coating of the capsules may also help to prevent unwanted side effects by premature release of the drug in the stomach.

Doesnâ?‚??„?t cause any irritation to the wall of the stomach.

dis advantages:

enteric capsules that are coated with chemicals have been developed to prevent the release of the drug in the stomach

how ever, the production process of enteric coating capsules involve the use of water and other solvents such as alcohol. Also during the drying process heat shock is applied. These agents may ccreate problem with the stability of the drug/material used.

Further, the capsules may not dissolve in the intestine if too muchof chemical coating is applied to the capsules.

Hence, for the manufacturing of the capsules highly skilled personal are required to control the coating process especially to avoid coating of the capsules. This may cause increase in the manufacturing.

1.2Hypermellose over gelatine:

The advantages of enteric capsules have overwhelmed the capsules made of gelatine. Gelatine capsules doesnâ?‚??„?t have enteric properties therefore, doesnâ?‚??„?t reach the intestine they get ingested in the stomach itself. Hence it is not recommended for the medication where it is supposed to be dissolved in intestine. It is pharmaceutically proven that medicinal substances show greater therapeutic values if they are absorbed from the upper portion of the intestine. Considering the potential advantages the known fact is that most of the medicaments are either absorbed from the stomach or destroyed rapidly for example penicillinâ?‚??„?s. Quinacrine and Sulfa drugs causes gastric disturbances. In order, to overcome these problems enteric coated capsules are preferred. Another use of enteric capsules is to prevent dissolution in stomach which in turn used for their effect in the intestinal region. Some examples of enteric capsules are aspirin, doxylamine, bisacodyl and sodium valporate (Okajima,1979).

Other than this many ethical issues has been arised regarding the gelatine capsules which was not recommended. Due to this problem there was a search for the materials which can substitute. Out which shinogi quai-v and capsugel V-caps are the currently marketed capsules. These capsules are formulated based on hypermellose. This hpmc are acceptable with respect to both the religious issues and also the dietry issues.(ing 4)

1.2 mechanism of drug release:

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after taking the capsule orally it is ingested inside into the body through peristaltic moment of the oesophagus. From oesophagues it reaches stomach which is a pouch like structure. From stomach it is transported to the duodenum. In the small intestime drug is released after 20-60 minutes which has a alkaline environment where the drug is absorbed through the intestinal wall into the stream of blood in the body.

To achieve rapid drug release in simulating upper intestine the dissolution of the enteric capsules have been accelerated. The in vitro dissolution studies of the capsule coated with polymers like cellulose esters,poly vinyl derivatives tec occur with in 30 minutes in pH 6.8 phosphate buffer(d catt)

But the gama invivo studies i.e gama scintigraphy showed that the duration of drug release from the capsule is after 2 hours(j r). initially drug is released in the distal part of the small intestine which results in delayed response and also potentially decreases the bioavailability for those drugs which has the absorption window in the proximal part of the small intestine.

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this difference between the in vivo and in vitro studies is due to the inadequacy of the commonly used dissolution medium which lacks the luminary conditions of the upper small intestine in may aspects like viscosity volume, buffer capacity, ionic composition and pH(c.shi). the enteric coating must be in such a way that it should be able to release the drugs in the small intestine. In order to facilitate the drug has been developed( fang).

The main reason for double coating the enteric capsules is that the dissolution of enteric capsules depends upon the ionization of the carboxylic acid groups of the enteric polymers at elevated pH. If the acid groups are neutralised to their ionised form then the dissolution rate is increased. Colonic drug delivery has gained increased importance not just delivery of the drugs for the treatment of local diseases of colon bt also for its potential for the delivery of proteins and peptides (gupta) colonic drug delivery is normally based on pH dependent system,time dependent delivery and system that utilises bacteria that colonize the colon or enzymes(rodi). Amongst all the approaches pH dependent system have found practical importance. The pH of GI tract gradually decreases from stomach (pH 1.5–3 ) to terminal ileum (pH 7-8). The pH at colon drops to 5.6 to 7 (evans). As the pH in terminal ileum and colon is higher than in any other regions of the GI tract. The drug which disintegrates at appropriate pH will have potential to the site specific delivery into the region. Methacrylic acid co polymers are the most commonly used pH dependent coating system. This methacrylic copolymer dissolves at pH 6-7.

Formulation variable

Process variable

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