Enteric coating is a process in which a layer of polymer is applied to the oral solid dosage forms to protect the drug release in the acidic environment of the stomach and to release the drug in alkaline pH in the small intestine.
Meant By Enteric Coating?
One commonly asked question is what is the meaning of enteric coating? so the answer is as follows,
The word enteric is related to the intestine and its meaning is within the intestine or affecting the intestine so enteric coating is any type of coating that ensures drug release in the intestine.
From above mentioned answer we can easily understand the answer of one more common question which is
Where do enteric coated tablets dissolve?
As we discussed earlier the enteric coated medicines are dissolved in the small intestine at basic pH.
How Does Enteric Coating Work?
- The basic mechanism or principle of enteric coating is pH dependent.
- The solubility of enteric coated polymer depends on the pH,so for enteric coating we use those polymers or material which are stable at acidic pH and does not dissolve, so protect the drugs from acidic environment.
- The polymers used for enteric coating dissolve easily at basic pH so the drug is released in alkaline pH of the intestine.
Advantages Of Enteric Coating / Why Enteric Coating?
In this part we will discuss advantages of enteric tablets or the enteric coated tablets that means why we use E.C tablets.
We use enteric coating for following reasons,
- To protect the drugs from acidic degradation in the stomach.
- Enteric coating enhances bioavailability of acid labile drugs.
- Some drugs may result in stomach ulcers so these drugs are coated with an enteric coat.
- Gastric irritations may result in nausea and vomiting so the drugs which may cause gastric irritations are enteric coated.
- Enteric coated medicines protect the mucosal layer of the stomach.
- Enteric coating is used to modify or alter the release of drugs meaning it is released in the small intestine instead of stomach.
- Enteric coated medicines are used to deliver maximum concentration of drugs in the small intestine.
Disadvantages Of Enteric Coating
- Enteric coating process increases the cost of the product because more coating material is required for enteric coating as compared to the film coating.
- More time is required for coating operation.
- Enteric coating requires skilled operators.
- Enteric coated tablets can not be crushed or broken down.
Enteric Coated Dosage Forms
Enteric coating also known as EC or gastro resistant coating can be done on following,
Enteric Coated Tablets
Tablets are most commonly used oral solid dosage forms and most of the tablets are available in film coating form to mask the taste and protect from humidity and temperature.
The active pharmaceutical ingredients which degrades in the stomach due to acidic pH or which may cause gastric irritations are not manufactured as film coated tablets rather these are available in enteric coating forms.
Enteric coated tablets are available in the market and are used for treating different disease conditions.
Most of the NSAIDs are coated with enteric coating to protect the stomach lining.
Enteric Coated Tablets Examples
Following are some examples of enteric coated tablets
Enteric Coated Aspirin Tablets
One of the most common examples is enteric coated aspirin tablets.
Enteric Coated Rabeprazole Tablets
Rabeprazole is used to treat GERD and is available in enteric coating form.
Other examples of enteric coated medicines are as follow,
- Diclofenac Enteric Coated Tablets
- Naproxen Enteric Coated Tablets
- Sulfasalazine Enteric Coated Tablets
- Erythromycin Enteric Coated Tablets
- Bisacodyl Enteric Coated Tablets
Enteric Coated Pellets
Enteric coated pellets are the type of dosage form in which we prepare the pellets and then these pellets are coated with enteric coating to protect the drugs from the acidic environment of the stomach.
Pellets are usually prepared by extrusion spheronization method and then a layer of enteric coat is applied by a fluidised bed processor.
Enteric Coated Pellets Capsules
The enteric coated pellets are filled in the empty hard gelatin shells to form enteric coated pellets capsules.
Enteric coated pellets are released in the stomach after dissolution of the gelatin shell.
The pellets remain intact in the stomach and release the drug in the basic pH of the small intestine.
Advantages of E.C pellets
- Drug release from pellets is rapid and high due to small pellet size.
- The stay time of pellets in the stomach is short as compared to the enteric tablets.
Examples Of Enteric Coated Pellets
Following are examples of enteric coated pellets
- Omeprazole Enteric Coated Pellets
- Esomeprazole Enteric Coated Pellets
- Lansoprazole Enteric Coated Pellets
- Pantoprazole Enteric Coated Pellets
- Aspirin Enteric Coated Pellets
- Rabeprazole Sodium Enteric Coated Pellets
Enteric Coated Granules
Granules can also be coated with the enteric polymer to protect the drugs from gastric acid.
Enteric Coating Process In Pharmaceutical Industries
The basic principle of Enteric coating process is the same as of film coating in which an automazed suspension of polymer is applied to the pre warmed tablets rotating in a coating pan.
The hot air is used which warms the tablets and solvent is evaporated so solid material continues to form a layer of polymer over the uncoated tablets.
Steps of Enteric Coating
Enteric coating is performed in the following steps,
- After checking average tablet weight and hardness the uncoated tablets are loaded into the coating pan.
- The tablets are de-dusted and prewarmed in the coating pan.
- If our product is moisture sensitive or we want to use an aqueous solvent for suspension preparation,first apply a sealing coat to protect the product from water penetration.Along with other coating materials a enteric coating polymer is used in the sealing stage.
- After seal coat, an aqueous coat is applied which also contains enteric coating polymer along with other coating materials.
- In enteric coating usually 10-12 % weight gain is achieved.
- The basic requirement is to apply such an amount of coating material over the tablets which gives protection to the tablets in an acidic environment.
- After achieving desired weight gain of coating materials the tablets are polished with a polishing material to give a shining appearance.
- After completion of the coating process the tablets are heated for a defined period of time and are cooled in the coating pan.
- Tablets are removed in containers after temperature normalization.
Enteric Sugar Coating
Enteric coating can also be done during sugar coating, meaning we can manufacture enteric coating sugar coated tablets.
For this purpose we make changes in the steps of sugar coating.
Steps Of Sugar Coating
First have a look over the steps of sugar coating which are as follow,
- Sub Coating
Process Of Enteric Sugar Coating
- For making a enteric coat sugar coated tablet we only make changes in the sealing step of sugar coating.
- In the sealing step we use an enteric coat polymer and apply such an amount of enteric coated polymer which makes our tablets stable at acidic pH.
- Remaining steps are the same as in the case of conventional sugar coating.
Stability Requirements Of Enteric Coating Tablets
The enteric coated tablets should not dissolve or disintegrate in acidic pH for 2 hours and should dissolve in basic pH within 1 hour.
Materials Used For Enteric Coating
One common question is what is used for enteric coating or which materials are used as enteric coating polymers.
So the following materials can be used as an enteric coating material,
- Cellulose Acetate Phthalate (CAP)
- Cellulose Acetate Trimellitate (CAT)
- HydroxyPropyl Methylcellulose Phthalate (HPMCP)
- Polyvinyl Acetate Phthalate (PVAP)
- Sodium Alginate
The first material used to make tablets enteric coat was Shellac but nowadays it is not used.
How To Take Enteric Coated Tablets
- Enteric coated tablets are swallowed as a whole with water.
- No crushing or splitting of E.C tablets into parts is recommended because if we break the tablets the protective enteric coating layer will be damaged and the core or uncoated tablet will be exposed.
- This exposed surface when it comes in contact with acidic pH starts dissolving because of the absence of a protective enteric layer.
- So always Take enteric coated medicines as a whole, not in broken parts.