A COMPREHENSIVE REVIEW ON COLON TARGETED DRUG …

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Singh et al. World Journal of Pharmacy and Pharmaceutical Science

A COMPREHENSIVE REVIEW ON COLON TARGETED DRUG

DELIVERY SYSTEM

Ajit Kumar Varma1, Neha Dubey

2, Gaurav Dubey

3, Jamshed Ali

4, Anurag Chourasia

5,

Akash Limba Kawale6 and Sahildeep Singh

7*

1Asst. Professor Department of Pharmaceutics, School of Pharmaceutical Sciences, Lingaya’s

Vidhyapeeth, Faridabad, Haryana. 2Department of Physiotherapy, Faculty of Paramedical Sciences Uttar Pradesh University of

Medical Sciences Saifai Etawah. 3Department of Optometry, Faculty of Paramedical Sciences Uttar Pradesh University of

Medical Sciences Saifai Etawah. 4Department of Optometry, Faculty of Allied Health Sciences, IIMT University Meerut Uttar

Pradesh. 5Department of Pharmacology, Uttarakhand Technical University, Dehradun, Uttarakhand. 6 Department of Pharmacy, Godavari Institute of Pharmacy, Kolpa, Latur, Maharashtra.

7*Department of Pharmacy, Amritsar Pharmacy College, Amritsar, Punjab.

ABSTRACT

Although significant interest in colon-specific drug delivery systems

has been placing over the past few years to create a delivery system

capable of releasing medications in the colon in a reliable and

replicable manner, these attempts have been unfruitful so far. The

colon is an area that can host both local and systemic medication

delivery. Drug administration should begin in the proximal colon and

be supported by protecting drugs against breakdown, absorption, and

release. The purpose of this evaluation is to grasp recent advances in

treatment approaches for dosage types that are currently designed to

administer colon therapies utilizing a pH-sensitive framework, a

microbially initiated system like prodrugs, and polysaccharide-based techniques.

KEYWORDS: Colon-specific drug delivery, pH-sensitive, time-controlled dependent,

microbially triggered, pressure controlled, and osmotically controlled system.

INTRODUCTION

Recent increases in colonic illness instances have prompted greater need for local colonic

disease treatment and have also given rise to better and safer treatment options. It is the most

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES

SJIF Impact Factor 7.632

Volume 10, Issue 10, 2322-2340 Review Article ISSN 2278 – 4357

*Corresponding Author

Sahildeep Singh

Department of Pharmacy,

Amritsar Pharmacy College,

Amritsar, Punjab.

Article Received on

21 August 2021,

Revised on 11 Sep. 2021,

Accepted on 01 Oct. 2021

DOI: 10.20959/wjpps202110-20721


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common colon ailment and is third on the list of cancers diagnosed. Among colon disorders,

colon cancer in Europe causes 200,000 deaths per year and is the deadliest of all colon

diseases. It is also becoming more common in Asia, where people had previously thought it

to be absent. Colon disease can be tough to deal with. A world with successful treatment is

one that they can survive in, and it is a goal all health care specialists are working toward. In

order to bring medicine to its target in the body (in this case, the colon) in an efficient manner

without adverse effects, researchers have created colon-targeted drug delivery technologies.

Because of a lack of protease activity in the upper GI tract, bigger proteins and peptides that

are common in pharmaceuticals have a harder time getting absorbed. In order to address this

problem, alternative methods like colon-targeted drug delivery systems that increase the

amount of bioavailable molecules in the GI tract are being tested. As with the tiny

compounds, more research might be done to prove colonic distribution's efficiency as an oral

delivery method for macromolecules. To provide colon-targeted drug delivery systems,

which deliver drugs only in reaction to the colonic environment and do not release any

medications in the upper GI tract, drug delivery systems have been designed to distribute

drugs only in response to the colonic environment. Microenvironmental factors and colon

characteristics must be accounted for when delivering drugs to the colon. There are several

things that change along the course of the GI tract, and some of them vary over different parts

of the tract. There is a considerable difference in the environmental characteristics of the

colon region with impacted tissue compared to the unaffected regions. Patients with

colorectal issues (RCs) generate extreme ROS and inflammatory cytokines. When this

happens, important antioxidants are impossible to synthesise, and the cells that make up the

mucosa become lacking, leading to substantial mucosal injury. Several methodologies for

increasing colonic medication delivery have been investigated, such as using pH-sensitive,

enzyme-triggered, and magnetically-driven devices. The strategy of going beyond local tissue

alterations was employed to create therapies, since changes in the area of disease must be

taken into account while planning treatments. A study focused on enzymes that interact with

a specific receptor in an area where the receptor is highly concentrated, unlike other enzymes.

This article is about recent formula advancements that have created colon-focused medicine

delivery systems, and how those delivery systems are used to treat diseases.


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Table 1: Colon targeting diseases, Drugs, and Sites.

Target sites Disease conditions Drug and active agents

Topical action

Inflammatory Bowel diseases,

Crohn’s disease,

Irritable bowel disease

Prednisolone, Budenoside,

Olsalazine,

Mesalazine,

Hydrocortisone,

Balsalazide, Sulfaselazine,

Local action

Chronic pancreatitis

pancreatectomy and cystic fibrosis

Colorectal cancer

Digestive enzyme

Supplements

5-Fluorouracil

Systemic action

To prevent gastric irritation

To prevent the first-pass

metabolism of orally ingested

drugs

Oral delivery of peptides

Oral delivery of vaccines

NSAIDS

Steroids

Insulin

Typhoid

Advantages of colon targeted drug delivery systems

Perfect for delivering a remedy to help heal Chron's disease, amoebiasis, ulcerative colitis

and other colon ailments.

There should be local treatment requirements for smaller medication amounts.

More minor drug interactions and adverse effects take place.

So, it is much more cost-effective. The extended colon retention period will help

medication molecules have better bioavailability in the body (up to 5 days).

Many medicines create a stomach irritation that can be avoided if kept from absorbing

into the GIT (e.g., NSAIDs).

You will save time by bypassing the first-pass metabolism of the digestive tract.

More long days and nights.

limits and hardships the distal region of the alimentary canal's difficulty of accessibility,

which is due to its position.

Dietary residues, digestive secretions, and fecal debris can bind to the medication and

limit its bioavailability.

Additionally, microorganisms in the colon degrade the drug, which could further disrupt

colonic functioning.

The low surface area and close connections in the colon keep the medicine from reaching

the systemic circulation via the mucosa because of the lack of space and closeness.

In-vitro dissolving tests are required to ensure that the dosage form is adequately

dissolved.


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A poorly soluble medication like the one required for efficient colon delivery will face

difficulties dissolving.

Considerations to keep in mind when planning for a CDDS.

It understands the anatomy and physiology of the colon.

Limitation of colon target drug delivery systems

Colon is challenging to reach.

Delivering medications must happen in solution in the colon, yet it is harder for poorly

soluble pharmaceuticals to dissolve in a viscous fluid environment.

A tight junction with lower surface area and relative tightness can hinder medication

delivery in the colon.

Need for colon targeting drug delivery

Localized treatment by colonic medication administration to assure lower doses and more

minor side effects overall

Targeted distribution of peptide and protein medications could be achieved via oral

administration.

A medicine delivery method that only affects the colon is thought to help fight colon

disorders.

The colon is the location of two possible delivery mechanisms for inflammatory bowel

disease (IBD) treatments such as ulcerative colitis and Crohn's disease: local therapy or

systemic treatment. Patients diagnosed with inflammatory disorders may have to take

glucocorticoids and sulphasalazine as part of treatment.

Colorectal cancer, and many other life-threatening disorders of the colon, may potentially

be treated more efficiently if medications were delivered explicitly to the colon.

Anatomy of the large intestine

An intestine component located below the stomach is often made up of four segments: the

cecum, colon, rectum, and anus. The term colon is also used to describe the big intestine in its

entirety.

The large intestine is around a meter and a half (about 5 feet) long and is broader and shorter

than the small intestine (around two-and-a-half times more expansive). Bacteria produce B12,

thiamin, and riboflavin in the upper large intestine, which completes the digesting process


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and supplies B vitamins. However, the large intestine's principal purpose is to extract water

and electrolytes from digesting debris (which takes around 24 to 30 hours) and store fecal

materials, then ejected them later. Digestive residues are gradually exposed to the absorbing

walls due to the churning of the large intestine. The gastrocolic reflex is a relatively short but

powerful and somewhat frequent action in the digestive system that pushes the waste matter

in the system to the rectum.

Fig. 1: Anatomy of the large intestine.

Diseases of colon

Diverticular condition: Weak areas in the intestinal wall, such as the diverticula, expand

colonic lining sacs. Where considerable bowel pressure is maximum (the sigmoid colon),

they tend to appear.

Crohn's disease: A digestive tract lining illness, common in older people, that is known to

persist in patients above the age of 55. Crohn's disease can create serious health problems that

can be fatal. Crohn's disease can suffer from abdominal pain, diarrhea, weight loss, anemia,

and exhaustion. Although some people never exhibit symptoms, those who do frequently

experience severe, long-term health problems.

Crohn's disease cannot be successfully treated. Steroids and immunosuppressants are used to

reduce the speed of the disease's progression. If these procedures aren't successful, the patient

will have to have surgery. People with Crohn's disease may need regular screening for

colorectal cancer because of the high risk of developing.


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Amoebiasis: An amoeba parasite that invades the colon, named Entamoeba histolytica.

People who live in places with unpurified water often get amoebic infections. Raw food such

as fruit washed in infected water can transmit the illness. Patients might experience moderate

cramping and diarrhea if the symptoms show up at all. Severe instances are likely to have

bloody stools, fever, and perhaps a liver abscess. Antibiotics are prescribed.

Colon bleeding: The color red indicates bleeding in the rectum or colon, leading to colon

cancer or rectal cancer. Bleeding in the rectum might be a symptom of hemorrhoids.

Diarrhea: Diarrhea is defined as loose or watery bowel motions. Diarrhea is characterized by

frequent loose, light bowel motions (or more frequently than usual). Diarrhea happens when

the intestines can't properly absorb or release water.

Colorectal polyps: A collection of cells that are built up around the colon or rectum's lining.

Some kinds are entirely safe, but others have the potential to become cancerous. Polyps

usually don't produce symptoms. Before cancer is allowed to develop, routine colonoscopies,

among other screening procedures, can be used to detect and remove polyps before they have

a chance to grow.

Colon cancer: A tumor found near the end of the intestinal tract, which starts in the colon or

rectum. Polyps are the earliest signs of colon cancer, which can begin as non-cancerous

polyps. It is possible to detect them even though they usually lack symptoms. In light of these

findings, doctors advocate routine testing for anyone at increased risk or above the age of 50.

The size and location of colorectal cancer can determine the symptoms experienced.

Symptoms such as bloody stools, bloating, and stomach pains are often found. To treat

colorectal cancer, it's essential to understand the characteristics of the disease and how far it

has progressed in the body. In cancer, people might expect surgery to get rid of it,

chemotherapy, and radiation treatment.

Approaches used for site-specific drug delivery to the colon

Methods used for site precise drug delivery are

1) Primary approaches for CDDS

a) pH-Dependent drug delivery systems

Altering the colon's acidity to make colonic medication distribution more effective is possible

by tackling the colon. Using CAP, HPMCP 50 and 55, Eudragit® S 100, Eudragit® L,


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Eudragit® FS, and Eudragit® P4135 F copolymers, it became possible to create a colon-

targeted drug delivery system. The use of copolymers for colonic medication delivery is

prevalent, with Eudragit polymers in particular providing mucoadhesiveness and pH-

dependent drug release. A truly ideal polymer must be able to hold together in the stomach

and upper small intestine but should thereafter begin to fall apart when in the lower small

intestine and colon. Polymers that have a pH sensitivity level of 6.0-7.0 have a coat solubility

threshold of 6.0-7.0. The polymer coat's dissolution properties will slow down the dissolution

of the drug and avoid premature drug release in the upper GI tract. In spite of its inherent

capabilities, this pH-dependent drug delivery system has low consistency, and it has proven

incapable of handling environmental changes, such as a patient's body pH, because it has

constant fluctuations.

Additionally, the pH in the GI tract can be strongly affected by factors such as the type of

food, an illness, how much water the person drinks, and the digestive processes of the

microbes there. Patients with ulcerative colitis, for example, show lower acidic intestinal pH

than healthy individuals, which reduces the effectiveness of enteric-coated medicines and

limits the amount of drug released at the target region. So, various internal and external

factors can mess with pH and negatively impact the efficacy of pH-dependent drug delivery

systems, with a poor site-selective drug release result. It was revealed that Eudragit® S

coating was not ideal for colon-targeted drug release either because the coating broke down

too soon, resulting in the colon being unable to hold the drug for any meaningful length of

time or because the layer broke down too late. The prescription was released in the colon

long before it could be absorbed into the bloodstream. Subsequent human investigations

showed the Eudragit S tablets lack site-selective drug release, showing disintegration of the

tablets is influenced by a variety of physiological parameters, including stomach pH, the food

the patient is taking, and the intestinal transit time.

In addition to time-dependent and enzyme-triggered delivery systems, there have been

several unsuccessful attempts to design systems which work regardless of pH, such as

systems which use delivery systems which rely on time or enzymes as a means of delivery,

and are paired with pH-dependent delivery systems. For example, systems made with high-

amylose maize starch and Eudragit® S broke down colon microbes at different pHs. For this

application, Eudragit® S was first combined with a high-amylose maize starch to form two

coatings, which were applied sequentially. An alkaline water and Eudragit S were initially


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sprayed on the starch in the first layer to keep it from degrading and to neutralise the starch's

pH. A buffer was then added to further protect the starch. Eudragit® S, a coating made with

organic ingredients, was used to speed medication breakdown at pH levels higher than 7. The

breakdown of dual-coated tablets was better in the lower GI tract after the approach was

studied and practised. They invented a delivery device that uses pH- and time-sensitive

microspheres to provide prednisolone to patients colonoscopically. They employed ethyl

cellulose and Eudragit® S to enhance colonic medicine administration and to reduce upper

intestine drug release. A multi-unit drug delivery system like Eudracol® that delivers

medications to the colon and leaves them there for release in equal amounts is an example of

a drug delivery method. There is a delivery mechanism that targets the colon that is activated

over time and in response to pH levels. Integrated systems utilising more than one method of

delivery, which can all be triggered based on pH, have been more successful than only pH-

controlled systems in dealing with pathological variability. However, more modifications are

required to achieve the desired result. Furthermore, it is thought that small particles may aid

to transport medication to inflammatory colon regions directly. To reach their target area in

the colon, many types of drug delivery systems have been designed using pH-dependent

components, which can make the particle they are connected to smaller.

b) Time-dependent or time-controlled system

Using a time-controlled method helps people administer their medications in the proper

locations and on their predetermined schedules. Diseases that are influenced by circadian

rhythms are often treated with the use of systems like this. Delayed-release formulations that

use a time-controlled delivery method for the colon are also known as "delayed-release

formulations" because of the delivery's use of a time-based period. The specific location of

drug release in these systems is based on the transit duration of a formulation in the GI tract,

making it challenging to create a formulation that will release a drug in the colon.

Formulations are, ideally, made to deliver where variation in stomach emptying time, pH in

the small intestine, or anaerobic bacteria in the colon won't interfere with the location. A drug

taken orally takes around three hours to transit from the small intestine to the colon. A tablet

form can launch a timed explosion in the colon and release the medicine. The concoction

consists of three elements:

(i) A center core containing swelling excipients and the treatment

(ii) A plasticizer that is included in an inner semi-permeable polymer barrier, allowing water

influx but preventing outward diffusion of medication


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(iii)Finally, an enteric-coating that dissolves at or above pH 5.5 is included as the outermost

layer.

The enteric coat, placed outside of the tablet, will keep it intact until it reaches the small

intestine. The enteric covering will break down when entering the small intestine, allowing

liquids to seep into the core. Consequently, the tablet bulges while traveling through the small

intestine. Lastly, after the firm orb had been in the small intestine for 4-6 hours, it would

expand and eventually explode, opening a hole in the semi-permeable membrane, through

which the medicine was released in the colon.

Fig. 2: Design of enteric-coated layer timed-release press coated tablet.

c) Microbially triggered drug delivery to colon

A millilitre of colonic bacteria has roughly 100 trillion germs. Bifidobacteria, Eubacteria,

Clostridia, Enterococci, Enterobacteria, Ruminococcus, and other anaerobic types are just

few of the species which are contained in its arsenal of bacteria. The small intestine is

deficient in digestive abilities, hence it contains lots of bacteria that can digest lots of

carbohydrates. Examples include polysaccharides (e.g., long chain carbs). There are a lot of

enzymes which can be created by the microflora in this fermentation. These include

glucuronidase, xylosidase, arabinoside, galactosidase, nitroreductase, azareducatase

deaminase, and urea dehydroxylase. To maximise colon-specific medicine administration,

biodegradable polymers are a preferred choice for enzyme compartments because they reduce

the chances of degradation of their polymeric medications. These polymer shields provide a


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barrier to protect the drug in difficult conditions, such as in the stomach and small intestine,

and help the medicine get to the colon and outside of the body. The molecular weight of the

colon can be reduced with enzymes or through microorganisms. Microorganisms grow in the

colon after turning it over. Reduced molecular strength means the equipment won't produce

much mechanical force. At that time, the drug entity cannot be halted.

(i) Approaches of prodrug for drug delivery to the colon

Colonic medicines undergo a minute hydrolysis in the upper intestines, and afterwards

enzyme hydrolysis in the colon to ultimately produce active drug moieties.

Limitations

a) Since it depends on the functional group of a chemical bond in the drug molecule, it

cannot be versatile.

b) Must be thoroughly evaluated before they can be deployed as carrier organizations.

(ii) Azo – polymeric prodrugs

When sub-synthetic polymers are utilised, a polymer containing an azo link between the

polymer and drug molecule is generated. Fig. 3 illustrates the azoreductase identified in the

large bowel to break down azo polymers.

Fig. 3: (i) Hydrolysis of Sulphasalazine (ii) 5- Aminosalicylic acid (iii) Sulfapyridine.

(iii)Polysaccharide based delivery systems

The polysaccharide polymer of monosaccharides resists enzymatic action because of its

integrity, so they are expected to retain their shape in the physiological environment of the

stomach and small intestine. When they reach the colon, the polysaccharides are worked on

by bacterial polysaccharides, thus degrading the matrixes. It is interesting to know that

natural polysaccharide's strength lies in the fact that it is more durable, safe, and less toxic


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than other polymers (Table 2). Pectin is a polysaccharide (long-chain sugar polymer) with

polygalacturonic acid, which contains galactose, arabinose, and rhamnose, with short side

chains of galactose and arabinose. A revolutionary approach to colonic medication

administration is evaluated. High methoxy pectin compressed on tablets is enzymatically

attacked in the gastrointestinal environment. Research using gamma scintigraphy confirmed

that in vitro tests showed that the pectin coating tablets disintegrated in the colonic region and

were degraded by microflora. This research needs to focus on devising new pectin derivatives

that are less water-soluble to meet consumer demand. Using the insoluble pectin salt, calcium

pectinate for colon-specific drug administration of Indomethacin was done. Turkoglu and his

colleagues studied colon delivery of the 5-aminosalicylic acid tablets, which were

compressed from pectin-hydroxy methylcellulose, and carried out degradation studies in

pectinolytic enzyme buffer pH 1.2 and 6.4. HPMC was necessary to stabilize the pectin

discovered on its own to be inadequate for supporting the structural integrity of the tablet.

Pectinase is a digestive enzyme that helps to break down fibrous material. When pectinase

was introduced to 6 hours of HPMC, the result was less than 30% erosion. The ichor from the

vessels would then slowly leak into the colon, releasing 5-amino salicylic acid.

Table 2: Characteristics of various biodegradable polymers for colon targeted drug

delivery.

Polysaccharide General properties Bacterial species

Amylose

Unbranched constituents of

starch used as excipients in

tablets formulation

Bacteriods, Bifidobacterium

Chitosan Deacetylated chitin is used as

absorption enhancing agent. Bacteroids

Cyclodextrin

The cyclic structure of 6,7 or

8 units, high stability against

Amylase, used as drug

solubilizing agent and

absorption enhancer.

Bacteroides

Dextran Plasma expanders Bacteroides

Arabinogalactan

Natural pectin,

hemicelluloses used as

thickening agents

Bifidobacterium

Guar gum Galactomman used as a

thickening agent

Bacteroids

Ruminococcus

Chondroitin sulfate

Mucosopolysaccharides

contains sulfate ester group at

4 or 6 position

Bacteroids


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2) Newly developed approaches for CDDS

a) Pressure controlled drug delivery system

Pressures of higher are found in the colon because of peristalsis. The team led by Takaya

created a colon-delivery capsule that uses ethyl cellulose and is insoluble in water to support

pressure regulation. Because of water reabsorption, the large intestine has more viscous

contents, which induce a more significant increase in luminal pressure than the small

intestine. To leverage colonic luminal pressure, studies have been done to devise colon-

specific medication delivery systems. A capsule containing the medicine is the main

component of the pressure-controlled drug delivery device. The polymer of water insoluble

ethylcellulose is applied to the inner side of the gelatin capsules, where the drug is added

along with a dissolving suppository base. When the capsules dissolve in the intestines, water

from the intestinal contents is absorbed, causing the gelatin to increase viscosity and rise in

pressure; this expulsion causes the drug to be released into the colon.

b) Pulsatile colon targeted drug delivery

i) Pulsincap system

Capsule systems (single units) are where they are usually developed. By eroding the stopper

inside the capsule, the medicine is "pulsed" out (control lag time). The drug capsule has a

hydrogel plug, which is compressed and inserted into the capsule. Once inside, the hydrogel

swells in the presence of a dissolution fluid. After a momentary delay, the swelling causes the

plug to push out of the capsule and quickly release the medication. How long the pin is and

where it goes into the tablet decides the length of the lag period.

ii) Port system

This technique utilizes delayed medication release as its fundamental premise. It has the

following parts:

Gelatin capsule housed in a cellulose acetate semi-permeable membrane

An insoluble plug (e.g., Lipidic)

A medication having an osmotically active ingredient added.


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Fig. 4: Plan of the port system.

c) CODES technology (Combination of pH-dependent and Microbially triggered

CDDS)

The CODES project was meant to circumvent the challenges presented by other solutions.

Microbially triggered approaches control where medication release takes place and also

provide control over the pH. A technique incorporating lactulose was utilized to create a

specific trigger that released drugs directly into the colon. The tablets are the core of the

machine, and it is made of a polymer coating applied to a base. To avoid the negatively

charged polymers from interacting, an enteric polymer coating is placed on top of an acid-

soluble polymer coating, with a layer of an HPMC barrier polymer placed in between. The

enteric coating of the tablet dissolves when it is positioned on the stomach, and then it shields

the tablet from gastric acids and pepsin while it's in the stomach. When the acidic soluble

material coating goes through the small alkaline intestine, it is protected. The bacteria

enzymatically degrade the polysaccharide (lactulose) into organic acid when the pill arrives

in the colon. The PH becomes lowered, which will reduce the coating's disintegration and the

drug's release. The polysaccharides are also in the center and work with the medication.

Tablet is made of mannitol, maltose, and similar substances. Bacteria found in the colon

break down polysaccharides, which are released from the middle of the tablet and then form a

coating over the medication to allow it to dissolve in the stomach.


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d) Osmotic controlled drug delivery

Osmotic drug delivery (designed by Alza Corporation) is an option for the delivery of

medicine to the colon just once and twice a day through a capsule. An OROS-CT is a multi-

faceted osmotic agent that can be used as a single agent or has between five and six osmotic

push-pull units in a gelatin capsule. After contact with GI fluids, the gelatin capsule

disintegrates, and the entry coating prevents fluids from the stomach into the system. The

water transport through the membrane happens with the disintegration of the layer in the

small intestine (that has a pH > 7).

Fig. 5: Cross-section of the OROS-CT colon targeted drug delivery system.

e) Multiparticulate system based drug delivery

These formulations contain several small individual units, each housing a powerful substance

to effectuate the release of medication, which is set off after a specific time interval via a set

of explosion-operated release mechanisms. Pellets, granules, microparticles, nanoparticles,

and beads are all included. The potential advantages of a multiparticulate system include:

• Fast, long-lasting results that stay in the body longer.

• Ensure complete absorption and even distribution in the gut.

• Fewer side effects overall, lower local irritation, and more controlled stomach emptying.


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Fig. 6: Multiparticulate drug delivery systems for controlled release.

f) Pro-biotic approach

Currently, techniques for targeting a person's colon use three things: an implant (a microbial

digestible carrier and Bifidobacterium and Lactobacillus), temperature triggering, and a

particular substance (e.g., microbeads). This strain can be activated in the body at standard

temperature, breaks down the drug-carrying vectors, and releases the medicine where needed.

With all of these conditions readily available in the colon, this strategy has had success.

Evaluation of colon targeted drug delivery system

In-vitro evaluation

An established method for determining if someone has CDDS is missing. An ideal in vitro

model must emulate the gastrointestinal system's pH, volume, bacteria, stirring, enzymes, and

enzyme activity. The results are dependent on your nutrition and your physical exercise. The

in-vitro dissolution and enzymatic tests are done on colon-targeted drug delivery devices.

In-vitro dissolution test

The dissolution tests are performed using the traditional basket method. To evaluate

formulations at various pH levels, dissolution testing is conducted in buffers of varying pH.

For the dissolution testing of colon-targeted drug delivery, several media are used, which

mimic gastric fluid (pH 1.2), small intestine (pH 6.8), and large intestine (pH 7.4). The colon-

targeted drug delivery devices are subjected to a series of three different environments, each

lasting two hours. The first environment is 0.1N HCl (pH 2.3), the second is phosphate buffer

(pH 6.8), and the third is pH 7.4 phosphate buffer. To measure colon-targeted drug delivery

systems, we have designed buffers of the above pH.


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In-vitro enzymatic test

For this, you must take two tests:

1. Allow the bacteria to grow while the antibiotics are in their medium (Streptococcus facial

or B.ovatus). We measured how much medicine was dispensed across various periods.

2. To analyze drug release, you use enzyme pectinase or rat or guinea pig or rabbit cecal

contents with your buffer solution. Release rates are tied to how quickly the polymer-

carriers degrade.

In-vivo evaluation

A variety of creatures, such as dogs, guinea pigs, rats, and pigs, are employed in experiments

that mirror the anatomic and physiological conditions of human gits, such as the presence of

bacteria. These species are utilized since they're most like the conditions in human GIT.

When considering the colonic disorders for an investigation, one should also think about the

option of a relative model. Guinea pigs are utilized frequently to provide an IBD model for

scientific purposes. There are quite a few similarities in azoreductase and glucuronidase

activity levels in rat, rabbit, and human digestive systems. A new model has been developed

for rapidly assessing CDDS. In this setup, human fetal bowels are transplanted under the skin

of nude mice. These can affect blood vessel growth in four weeks, mature, and eventually

gain the ability to create a mucosal immune system.

CONCLUSIONS

Better delivery techniques are needed for localized disorders of the colon that address the

existing medications. In contrast to a conventional drug that is dispersed in the whole body, a

drug that targets only the colon is more likely to have side effects and needs to be more

robust to be effective. This way, you don't need a dose as high to be effective, which also

means that there will be less medicine in the body.

Because these materials are non-toxic, economically friendly, and chemically compatible

with other ingredients, interest in biodegradable polymers is constantly expanding. The

biodegradable polysaccharides in colon-specific medication delivery have been previously

discussed in this article. Polysaccharides are the building blocks of a colonic delivery system

with attractive characteristics. Microflora found in the colon is an attractive target for

medication release in that region. Microbial degradable polymers used to create the drug's

formulation are discharged from the upper GIT and pass through intact before being excreted


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in the colon. Polysaccharides seem capable of delivering colon-specific drugs, a prospect that

has researchers excited.

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