Colon Targeted DDS Flashcards
What are the Advantages of CTDDS over
conventional drug delivery? (4)
Reduce the adverse effects in the treatment of colonic diseases (ulcerative colitis, colorectal cancer, crohn’s disease)
Produce the ‘friendlier’ environment for peptides and proteins as compared to upper gastrointestinal tract
Prevent the gastric irritation produced by oral administration of NSAIDS.
Delayed release of drugs to treat angina, asthma and rheumatoid arthritis
What are the Limitations of CTDDS
the fluid content in the colon is lower and more viscous than in upper GIT, which is the limiting factor for poorly soluble drugs.
Lower surface area and relative tightness of the tight junctions in the colon can restrict drug transport across the mucosa into the systemic circulation
what can we use to facilitate absorption of drug from colon?
Permeation enhancers
What drugs are Candidates for CTDDS
Drugs showing poor absorption from stomach/ intestine including peptides
Drugs use in treatment of IBD amobiasis colon cancer…
Drug should be compatible with carrier molecule (prodrug)
Should be stable at alkaline pH of GIT
Do I include permeation enhancer iza ana bede local action?
NO
Approaches for colon targeting (6)
- Conjugated prodrug
- Probiotic approach
- Coating with pH sensitive polymer
- pH sensitive hydrogel
- Time dependent drug delivery
- Pressure controlled drug delivery
1) Conjugated Prodrug
What are the types of conjugation
Azo bond
Glycoside
Glucuronide
What is an Azo bond conjugation
Azo bond is stable in the upper GIT
Cleaved in the colon by azo-reductase produced by microflora
e.g. Sulfasalazine
What is a Glycoside Conjugated prodrug
Glycosides are used as carriers for delivering drug to colon
e.g. dexamethasone-21-b-glucoside and prednisolone-21-B-glucoside
Glucuronide Conjugated prodrug
Specifically cleaved by B-Glucuronidases on the colon
i.e. glucuronide conjugation of narcotic analogs
Naxolone and nalmefene used in the treatment of constipation caused by opiate
2) Probiotic Approach
What are its components
Three components are desirable:
Probiotic strain
Microbially digestible carrier
Triggering temperature
What are Probiotic strains
Inactive microflora like bifidobacterium and lactobacillus
At body temp these strains get active and start digesting the carrier so the drug is released
3) Coating with pH sensitive polymer Approach
E.g. of ph dependent polymer
Emtan starts to release drug
Coating the tablet with pH dependent polymer
e.g. Eudragit S and L
The polymer remains intact in stomach bur start releasing small amounts at the distal part of s.intestine
As it enters the colon, the entire coat is dissolved and drug is released
The difference between Eudragit S and L
L ph>6 (aLkaline)
S ph<6
What is the major limitation of pH sensitive polymer (2)
It is contorlled by polymer coat thickness
Premature release can occur