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Colon – Specific Drug Delivery SystemColon – Specific Drug Delivery System
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CONTENTS•IntroductionIntroduction•Anatomy & Physiology of Colon•Factors governing the colon drug delivery•Colon absorption•The major functionsThe major functions•AdvantagesAdvantages•Pharmaceutical Approaches for Targeting Drugs to Colon•Platform Technologies for CTDDS•Evaluation•Conclusion
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Introduction:
Colon as a site for drug delivery.
Colon was considered as BLACK-BOX as most of the
drugs are absorbed from upper part of the GI tract.
The site specific delivery of drugs to lower parts of the GIT
is advantage for localized treatment of several colonic
diseases(IDB).
The CDDS drug release and absorption should not occur in
the stomach as well as small intestine, but only released and
absorbed once the system reaches to the colon.
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Why is CDDS needed?Why is CDDS needed?
Ensure direct treatment at the disease site.
Lower dosing and less side effects.
Beneficial in the treatment of colon diseases.
Suitable absorption site for protein and peptide
drugs.
Used to prolong the drug therapy.
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Anatomy & Physiology of Colon
GIT: •Stomach•Small intestine•Large intestineCOLON:
Colon Rectum
Anal canal
Colon consists:• Cecum• Ascending colon• Transverse colon• Descending colon• Sigmoid colon
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•Serosa
•Muscularis
externa
•Submucosa
•mucosa
Layers:
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Factors governing the colon drug delivery
Gastrointestinal transit
Small intestinal transit
Colonic transit
Gastric emptying
Stomach and intestinal pH
Colonic micro flora and enzymes
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pH of GIT:pH of GIT:LOCATION Ph
1.STOMACH:
Fasted
Fed
1.5-2.0
3.0-5.0
5.0-6.5
2.SMALL INTESTINE:
Jejunum
Ileum
6.0-7.5
6.4
6.7-7.3
3.LARGE INTESTINE:
Right colon
Mid colon
Left colon
6.5-7.0
6.6-7.0
6.6
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Drug absorption in the colonDrug absorption in the colon
Drug molecules pass from the apical to
basolateral surface of the epithelial cell by
1. Transcellular - Passing through colonocytes.
2. paracellular - Passing between adjacent
colonocytes.
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The major functions The major functions
The absorptive capacity is very high; each day about 2000 ml of fluid enters the colon through the ileocecal valve from which more than 90% of the fluid is absorbed.
Creation of a suitable environment for the growth of colonic microorganisms, such as Bacteroides, Eubacterium, and Enterobacteriaceae.
Expulsion of the contents of the colon at a suitable time.
Absorption of water and Na+ from the lumen, concentrating the fecal content, and secretion of K+ ions
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AdvantagesDrugs are directly available at the target site.
Comparatively lesser amount of required dose.
Decreased side effects.
Improved drug utilization.
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Pharmaceutical Approaches for Targeting Drugs to Colon
pH sensitive systemsMicrobially triggered system
◦Prodrugs ◦Polysaccharide based systems
Timed release systemsOsmotically controlled drug
delivery systemsPressure dependent release
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pH sensitive systems
Solid formulations for colonic delivery that are based on pH-dependent drug release mechanism are similar to conventional enteric-coated formulations.
Utilize enteric polymers that have relatively higher threshold pH for dissolution.
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Polymers
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Mechanism of actionMechanism of action
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Microbially Triggered Systems
Bacterial count in the colon is much higher around 1011-1012 CFU/ml.
400 species Fundamentally anaerobic in
nature. Predominant species:
Bacteroides, Bifidobacterium and Eubacterium.
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Major metabolic processes occurring in the colon are hydrolysis and reduction
Enzymes in Colon
Reducing enzymes Hydrolytic enzymesNitroreductase EsterasesAzoreductase AmidasesN-oxide reductase GlycosidasesSulphoxide reductase GlucuronidaseHydrogenase Sulfatase
Azoreductases, which reduces azo-bonds selectively andPolysaccharidases which degrades the polysaccharides
.
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Azobond prodrugs
Hydrolysis of sulphasalazine (i) into 5-aminosalicylic acid (ii) andsulfapyridine (iii).
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Glycoside conjugates
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Natural Polysaccharides as Polymer
for Colon Drug Delivery
Chitoson Pectin Guar gumChondroitin sulphateDextran Almond gum Locust bean gumCyclodextrins Inulin Boswellia gumKhaya gum
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Enteric-coated polysaccharide matrix
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Compression Coated Tablets
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Mixed Film Coated Tablets
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Timed Release Systems
Releases the drug after a predetermined lag time
The lag time usually starts after gastric emptying because most of the time- controlled formulations are enteric coated
Drug release from these systems is not pH dependent
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Osmotically Controlled Drug Delivery Systems
Depend up on the osmotic pressure exerted by Dependosmogen on drug compartment with which though drug get released slowly though the orifice
Rigid semi permeable membraneOsmotic agent layer
Delivery port
Fluid to be pumped
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Pressure Dependent Release Systems
Relies on the relatively strong peristaltic waves
in the colon that lead to an increased luminal
pressure, in response to raised pressure of the
colon the dosage form get ruptured and release
the drug at desired site
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Platform Technologies for CTDDS
• PULSINCAP
• OROS-CT
• CODESTM
• CHRONOTROPIC® SYSTEM
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PULSINCAP
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OROS-CT
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CODESTM
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CHRONOTROPIC® SYSTEM
Drug containing core
HPMC Coat
Enteric coat
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EvaluationInvitro modelsInvitro test for intactness of coating and carriers in simulated
conditions of stomach and intestine
step1
Drug release study in 0.1N HCL for 2 hours (mean gastric emptying)
step 2
Drug release study in phosphate buffer for 3 hours (mean small intestine transit time)
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In vitro enzymatic degradation test
Method 1:
Drug release in buffer medium containing enzymes(e.g.pectinase, dextranase) or rat or guinea pig or rabbit decal contents
Amount of drug release in particular time directly proportional to the rate of degradation of polymer carrier.
Method 2:
Incubating carrier drug system in fermenter
Suitable medium containing colonic bacteria (streptococcus faecium or B.ovatus)
Amount of drug released at different time intervels determined.
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Clinical evaluation of colon-specific drug delivery system
• Gamma Scintigraphy
• High-frequency capsule
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Gamma Scintigraphy showing the spread of the tracer allalong the ascending, transverse, descending and sigmoidcolon
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High-frequency capsule High-frequency capsule method:method:The relative BA of CDDS can be evaluated by high
frequency capsules smoth plastic capsule containing
small latex bollon, drug and radiotracer taken orally
Triggering system (high frequency generator)
Release of drug and radiotracerTriggered by an impules, the release is monitered
In different parts of GIT byRadiological localization
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Conclusion
The colonic region of the GIT has become an increasingly important site for drug delivery and absorption.
CDDS offers therapeutic benefits to patients in both local and systemic treatment.
Systems utilize natural materials that are degraded by colonic bacterial enzymes.
Colon provides favorable factors and conditions for designing of delivery systems.
High commercial viability. Increasing number of international patents and research work in this particular mode of drug delivery itself shows its potential for pharmaceutical market.
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S.P. Vyas, R.K. Khar ; controlled Drug DeliveryN.K.JAIN; Progress in controlled and novel drug
delivery systems.Vincent H.L. Lee and Suman k. Mukherjee ;
Encyclopedia of pharmaceutical Technology. Edi 2007Van den Mooter G. V., Kinget R, (1995) Oral colon-
specific drug delivery: a review DrugDeliv, 2: 81-93.Sarasija S, Hota A. (2002) Colon-specific drug delivery
systems. Ind J Pharm Sci. 62(1):1-8.Colon targeted drug delivery system: A Review on
primary and novel approaches.Oman Medical J,volume 25, issue 2, april2010.
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Colon-specific drug delivery system: IJPS,2000,62,1-8.
Oral colon targeted delivery systems for treatment of IBD: synthesis,in vitro and invivo assessment-IJPharm 358(2008)248-255.
Novel Pharmaceutical Approaches for Colon Drug Delivery: An overview- Journal of Pharmacy Research, july-sep 2008
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THANK YOU
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