Presented by:
Rohitkumar Subhash Rathi
Roll No: 89
Batch: D
Guided by: Sahebrao Boraste
Class: Final Year B-pharm
GES’s Sir.Dr.MSG COPER, Nashik
Presented by:
Rohitkumar Subhash Rathi
Roll No: 89
Batch: D
Class: Final Year B-pharm
GES’s Sir.Dr.MSG COPER, Nashik

 CONTENTs
 Introduction
 Criteria of drug selection
 Advantages & Limitations/
Challenges/Difficulties
 Approaches of colon targeting
 Evaluation
 Reference

 INTRODUCTION
 Targeted drug delivery systems:
 The major goal of any drug delivery system is to supply a therapeutic
amount of drug to a target site in a body.
 Targeted drug delivery implies selective and effective localization of
drug into the target at therapeutic concentrations with limited access to
non target sites.
 A targeted drug delivery system is preferred in drugs having instability,
low solubility and short half life

 Definition:-
Colon drug delivery system refers to targeted delivery of drug in to the
lower parts of GI tract, mainly large intestine.
Targeted delivery of drugs to the colon is usually to achieve one or
more of four objectives:
1) To reduce dosing frequency
2)To delay delivery to the colon to achieve high local concentrations
in the treatment of diseases of the distal gut,
3)To delay delivery to a time appropriate to treat acute phases of
disease (chronotherapy)
4)To deliver to a region that is less hostile metabolically, e.g., to
facilitate absorption of acid and enzymatically labile materials,
especially peptides.

WHY COLON TARGETED DRUG
DELIVERY IS NEEDED?
 As most of the conventional drug delivery systems for treating colon
disorders such as inflammatory bowel diseases, infectious diseases
and colon cancer are failing as the drugs don't reach the site of action
in appropriate concentration.
 Thus an effective and safe therapy of these colonic disorders using
site specific drug delivery system.
 The therapeutic advantages of targeting drug to the diseased organ
include,
a) Delivery of drug in its intact form as close as possible to the target
site.
b) The ability to cut down the conventional dose.
c) Reduced incidence of adverse side effects.

In recent times the colon-specific delivery
systems(CSDDS) are also gaining importance for the
systemic delivery of protein and peptide drugs. This is
because,
i) as the peptide and protein drugs are destroyed and
inactivated in acidic environment of stomach or by
pancreatic enzymes (or) by parenteral route which is
inconvenient and expensive.
ii) Due to the negligible activity of brush border membrane
peptidase activity and less activity of pancreatic enzymes
the colon is considered as the most suitable site.

ADVENTAGES
 The site specific delivery of drug to lower part of GIT, for localized treatment of several
colonic diseases. (ulcerative colitis, Chron's disease, carcinomas and infections)
 Prevent drug from degradation.
 Ensure direct treatment at disease site.
 Suitable absorption site for Protein & Peptide drug.
 Used to prolong the drug therapy.
 Improved drug utilization.
Limitations / Challenges/Difficulties
 Multiple manufacturing steps.
 Microflora affects activity of drug via metabolic degradation of the drug.
 Bioavailability of drug may be low due to potentially binding of drug in a nonspecific
way to dietary residues, intestinal secretions, mucus or faecal matter.
 Non availability of an appropriate dissolution testing method to evaluate the dosage
form in-vitro.

Application
 In local colonic pathologies
 Systemic delivery of protein and peptide
 Potential site for the treatment of diseases sensitive to
circadian rhythms (asthma, angina and arthritis)
 For the drugs that are absorbed through colon such as
steroids (….efficacy..)
 For the treatment of disorders like IBS, colitis, crohn’s
disease (…where it is necessary to attain high
concentration of drugs

Colon targeting diseases, drugs and sites

Criteria of drug selection
 Drugs used for local effects in colon against GIT
diseases.
 Drugs poorly absorbed from upper GIT.
 Drugs for colon cancer.
 Drugs that degrade in stomach and small intestine.
 Drugs that undergo extensive first pass metabolism.
 Drugs for targeting.

Pharmaceutical Approaches for
Targeting Drugs to Colon
 An oral colonic delivery system should retard drug release in the stomach
and small intestine but allow complete release in the colon.
 A variety of strategies has been used and systems have been developed for
the purpose of achieving colonic targeting.
1) pH sensitive systems
2) Microbially triggered system
Prodrugs
Polysaccharide based systems
3) Timed release systems
4) Osmotically controlled drug delivery systems
5) Pressure dependent release systems

EVALUATION
 For evaluation, not any standardized evaluation technique is available for
evaluation of CDDS because an ideal in vitro model should posses the in-vivo
conditions of GIT such as pH, volume, stirring, bacteria, enzymes, enzyme activity,
and other components of food.
 These conditions are influenced by the diet, physical stress, and these factors
make it difficult to design a standard in-vitro model.
1.In vitro dissolution study
2. In vitro enzymatic degradation test
3. Relative colonic tissue exposure
4. Relative systemic exposure to drugs
5. Scintigraphy
6. Magnetic moment imaging study
7. Drug delivery index
8. High frequency capsule

1. In vitro methods:
 The ability of the coats/ carriers to remain in the physiological environment of the
stomach and small intestine is generally assessed by conducting drug release
studies in,
• Drug release study in 0.1 N HCl for 2 hours (mean gastric emptying time)
• Drug release study in phosphate buffer for 3 hours (mean small intestine
transit time PH 6.8)
 These dissolution studies can be carried out by using paddle or basket or flow
through dissolution apparatus.
IN-VITRO DISSOLUTION TEST
Dissolution of CDDS is usually complex, dissolution Describe in USP.
Disso. Carried out by conventional basket method.
Dissolution tests for CDDS in different media simulating pH condition times likely
to be encountered at various location in GI tract.

Bio-Dis-III (Apparatus III)
• Ideal for the dissolution profiling of extended release dosage forms.
• It is designed to meet or exceed current USP specification.
• It used a reciprocating motion to dip the inner tube into media.
• At the designated time, the entire row of inner tubes raises and moves to the next
row of media.
• Capable of running unattended upto 6 days and can store upto 25
programs.
• 7 sample tubes which automatically traverse upto 6 rows of
corresponding outer tubes filled with different media.
• With accessories, the appropriate media volume can vary
from 100, 300 ml (USP) or 1000 ml.

In vitro enzymatic degradation test
 Method 1:
Drug release in buffer medium containing enzymes(eg. 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 intervals determined.

2 In vivo methods:
 Animal models
• Rats, mice, pigs and dogs animal models were reported for colon
targeted drug delivery systems.
• For simulating the human physiological environment of the
colon, appropriate animal model selection is depends on its
approach and design of system.
• For example, guinea pigs have glycosidase and glucuronidase
activities in the colon and digestive anatomy and physiology is
similar to that of human, so they are appropriate in evaluating
prodrugs containing glucoside and glucuronate conjugated for
colonic delivery.

Techniques which are used for monitoring the in vivo
behavior of colon targeted drug delivery are:
1) String technique
2) Endoscopy
3) Radiotelemetry
4) Roentegenography
5) Gamma scintigraphy.

Reference
 Colon Targeted Drug Delivery System: A review on A
review on primary and novel approaches by Threveen challa,
Vinay vynala.
 Colon Targeted Drug Delivery System: A review on the
pharmaceutical approaches with Current Trends by
Cherukuri Sowmya.
 Colon Targeted Drug Delivery System: A novel perspective
by bhushan prabhakar kolte.