The document discusses drug absorption from the gastrointestinal tract. It covers the functions of the GI system including motility, secretion, digestion and absorption which influence drug uptake. It also discusses physiological properties of GI smooth muscle, gastrointestinal hormones, factors that can destroy drugs in the GI tract before absorption like gastric acid and enzymes. It explains drug absorption via the portal circulation and liver and concepts like pH partition hypothesis and how pH affects drug absorption. Finally, it briefly mentions tight junctions and their functions in the intestinal epithelium including forming a barrier and maintaining cellular polarity.

1. Drug Absorption from the
Gastrointestinal Tract
Presented by-
Manohar D Kengar,
Dept.of
pharmaceutics
M.pharm FY
Rajarambapu
College of Pharmacy
Kasegaon
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2. Functions of gastrointestinal
system
• Motility of GIT: Drugs are better absorbed in
normal GIT movement.
• Secretion: release of digestive juices in response to
a specific stimulus.
• Digestion: breakdown of food in to molecular
component small enough to cross the plasma
membrane. example: propranolol.
• Absorption: passage of the molecules in to the
body’s interior and their passages throughout .
• Elimination: removal of undigested food and
wastes.
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3. Physiological properties of
gastrointestinal smooth muscle
General properties-
•Low excitability
•High distensibility
• Tonic contraction
•Autorhythmicity
•High sensitivity to temperature ,stretch
and chemical stimulation .
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4. Gastrointestinal hormones
The hormones synthesized by a large number of
endocrine cells within the gastrointestinal
tract
Physiological function
• Control of the digestive function
• Control of the release of other hormones
• Tropic action
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5. Destruction of drug in GIT
In GIT, there are gastric HCL, enzymes
etc.
So, drugs may be destroyed in GIT before
absorption.
Example:
•Benzyl penicillin in destroyed by gastric
HCL
•Insulin is destroyed by proteolytic1/30/2018 5

6. Absorption from GIT
Portal circulation
Liver
Systemic circulation
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7. pH partition
hypothesis
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Unionised drug Higher Absorption
IONISED DRUG LOW ABSORPTION

8. Effect of pH on drug
absorption
•Acidic drug better absorbed in acidic media.
•Basic drug better absorbed in basic media.
•Acidic drug (Aspirin) are better absorbed in
stomach (in acidic media)
and
•Basic drug (Diazepam) are better absorbed in
intestine (in alkaline media)
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9. •Acidic drug better excreted in acidic
media.
•Basic drug excreted in basic media.
•Incase of the acidic drug poisoning
alkalization done to promote excretion of
the drug.
and
•Incase basic drug poisoning acidification
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10. Tightjunctioncomplex
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11. Functions of tight junction
• They hold together
•Barrier function ,which can be further
subdivided in to protective barrier and
functional barrier serving purpose
such as material transport and
maintenance of osmotic balance.
•It help to maintain to polarity of cell.
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12. reference
1. ‘Cell Junction’, presented by Dr.
Shaimaa, PG oral pathology.’
2. ‘Gastrointestinal physiology’, by
Liang Huawei, Ph.D.’
3. Internet by Wikipedia.
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