short description of the factors that influence drug absorption.

1. -BY APUSI CHOWDHURY
23rd BATCH

2. Content
Drug absorption
Influencing factors
Physiological factors
Physicochemical nature of drug
Pharmaceutical factors
Effect of disease states on drug
absorption
GI content affecting absorption
Drug-food interaction affecting
absorption
Drug-drug interaction affecting
absorption
Effect of excipients
References

3. Drug absorption

4. The process of movement of
unchanged drug from the site
of administration to systemic
circulation.

5. Drug
absorption
influencing
factors

6. Physiological
factors
Pharmaceuti
cal factors
Physicochemical
factors
Drug
absorption
factors

7. Physiological
factors

8. • Route of administration
• Membrane physiology
– Nature of cell
membrane
– Transport process
• Age
• Gastric emptying time
• Intestinal transit time
• Gastrointestinal pH
• Disease states
• Blood flow through the
GIT
• Gastrointestinal
contents:
– Food- drug
interactions
– Fluids
– Other normal GI
contents
• Pre-systemic
metabolism by:
– Luminal enzymes
– Gut wall enzymes
– Bacterial enzymes
– Hepatic enzymes

9. Physicochemical
factors

10.  Drug solubility & dissolution rate
 Particle size & effective surface
area
 Polymorphism & amorphism
 Pseudopolymorphism
(hydrates/solvates)
 Salt form of the drug
 Lipophilicity of the drug (pH-
Partition-hypothesis)
 pKa of drug & gastrointestinal pH

11. Pharmaceutical
factors

12. 1) Disintegration time
(tablets/capsules)
2) Dissolution time
3) Manufacturing variables
4)Pharmaceutical ingredients
(excipients/adjuvants)
5) Nature & type of dosage form
6) Product age & storage condition

14. s1Drug absorption may be affected by any
disease that causes changes in the:
Intestinal blood flow
Gastro intestinal motility
Stomach emptying time
Gastric pH that affects drug
solubility
Intestinal pH that affect ionization
Gut wall permeability
Bile secretion
Digestive enzyme secretion
Alteration of GI flora

15. Gastrointestinal
contents
affecting
absorption

16. Altered absorption
Interaction
between
drug &
normal GI
contents
Food -drug
interaction
Drug -drug
interaction

17. Drug-food
interaction

18. Absorption of water soluble vitamins, such as
vitamin B-12 & folic acid, are aided by special
absorption mechanism.
Grapefruit juice often increases bioavailability,
as observed by an increase in plasma levels of
many drug that are substrates for cytochrome
p-450 (CYP) 3A4.
In general presence of food either delay,
reduce, increase or may not affect absorption.
Aspirin Delayed
Penicillin Decreased
Griseofulvin Increased
Methyldopa Unaffected

19. DRUG-DRUG INTERACTION
AFFECTING ABSORPTION

20. PropanthelinDigoxcin
Antacid Cimetidine
Cholestryamine Warfarin
absorptionabsorption

21. Interaction
of drug
with GI
content

22. • GIT contains no. of normal constituents such
as mucin, bile salts and enzymes, which
influence the drug absorption.
E.g.
Bile salts
Increase absorption of Vitamins (Solution)
Decrease absorption of Neomycin and Kanamycin
(Insoluble complex) .
Intrinsic factor enhances vit B-12 absorption.

23. Effect of excipients

24. Excipients Example Ka Tmax AUC
Disintegrants Avicel,
Explotab
Lubricants Talc,
Hydrogenated
vegetable oil
Coating
agent
Hydroxypropyl
methyl cellulose
Enteric
coating
Cellulose
acetate
phthalate
Sustained
release agents
(waxy agents)
Castorwax,
carbowax
Sustained
release agents
(gum/viscous)
Veegum,
keltrol

25. REFERENCES
1. Brahmankar D.M., Jaiswal S.B., First edition, “Absorption
of Drugs” Biopharmaceutics and Pharmacokinetics – A
treatise, Vallabh Prakashan, Delhi 1995.
2. Shargel L., Andrew B.C., Fourth edition “Physiologic
factors related to drug absorption” Applied
Biopharmaceutics and Pharmacokinetics, Prentice Hall
International, INC., Stanford 1999.
3. Aulton M.E. Pharmacetutics “The Science of Dosage Form
Design”, 2nd Ed.; Churchill Livingstone.