FACTORS AFFECTING DRUG
ABSORPTION
Name: Suraj Mandal
M.Pharm (Ist year)
Advanced Pharmaceutics.
NKBR COLLEGE OF
PHARMACY & RESEARCH
CENTRE, MEERUT
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LIST OF CONTENTS:
• INTRODUCTION OF ABSORPTION
• TRANSPORT PROCESS
• FACTORS AFFECTING DRUG ABSORPTION:
1)Physiological factors
2)physiochemical factors
3)pharmaceutical factors
• REFERENCES
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ABSORPTION:
• Definition: The process of movement of
unchanged drug from the site of
administration to systemic circulation.
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TRANSPORT PROCESS:
• PASSIVE DIFFUSION
• PORE TRANSPORT
• FACILITATED DIFFUSION
• ACTIVE TRANSPORT
• PINOCYTOSIS
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1.PHYSIOLOGICAL FACTORS:
• AGE
• GASTRIC EMPTYING
• INTESTINAL TRANSIT
• GASTRO INTESTINAL PH
• DISEASE STATE
• GASTRO INTESTINAL CONTENTS
• PRESYSTEMIC METABOLISM.
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AGE:
• In children & Infants Gastric pH is high and intestinal
surface and flow to git is low.
• while in adults altered gastric emptying, decrease
intestinal surface area, decrease gastric blood flow &
higher incidence of achlorhydria cause impaired drug
absorption.
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Gastric emptying:
• Gastric emptying is the passage of drug from
stomach to small intestine.
• Gastric emptying is delayed when co-administered
with food.
• Factors that influence G.E are :volume of meal,
composition of meal, physical state and viscosity of
meal, temperature of meal, body posture, exercise
,disease state etc.
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Intestinal transit time:
• Since, intestine is the major site of absorption
of most of the drugs, Long intestinal transit
time is desirable for the complete absorption
of drugs.
• Delayed intestinal transit is desirable for :
--Drugs that dissolve only in intestine (enteric coated ).
--Drugs absorbed from specific sites in the intestine.
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Gastro intestinal PH:
• A difference in PH is observed between gastric
and colon fluids. The GI PH increases gradually
from stomach to the colon and rectum.
• The PH of GI fluids influence the drug
absorption in several ways:
-dissolution
-stability.
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DISEASE STATE:
• GI Disease: Infection such as Achlorhydria,
malabsorption and surgeries such as
gastrectomy affect the absorption of drugs to
a greater extent.
• Disorders such as hepatic cirrhosis influence
bio-availability mainly of drugs that undergo
considerable first-pass hepatic metabolism
e.g. Propranolol
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2)Physicochemical factors:
• DRUG SOLUBILITY & DISSOLUTION RATE.
• PARTICLE SIZE
• POLYMORPHISM &AMORPHISM
• PSEUDOPOLYMORPHISM
• SALT FORM OF THE DRUG
• Pka OF THE DRUG
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Particle size:
The absorption of the drug can be increased by increasing the
particle surface area by micronization.
Smaller the
drug particle
Greater the
surface area
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Polymorphism and amorphism:
•When substance exists
in different crystalline
forms it is polymorphism.
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AMORPHISM:
• They have greater aqueous solubility than the
crystalline forms because the energy required
to transfer a molecule from crystal lattice is
greater than that required for the non
crystalline solid.
• Eg:Novobiocin
• The order of Dissolution & hence Absorption
for different solid dosage forms is
amorphous > meta-stable > stable.
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3)Pharmaceutical factors:
• MANUFACTURING VARIABLES:
-Method of granulation
-Compression force.
• NATURE AND TYPE OF DOSAGE FORM.
• PHARMACEUTICAL INGREDIENT AND
EXCIPIENTS.
• STORAGE CONDITIONS.
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Manufacturing variables:
1)Method of granulation: The method of dry
granulation can be used to produce tablets that
dissolve at a faster rate.
2)compression force: Influence the hardness,
density,porosity,disintegration,dissolution of
tablet.
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Nature and type of dosage form:
• Bioavaibility of a drug from various dosage
form is in the following order:
• solution>emulsion>suspension>Capsules
>tablets>coated tablets>enteric coated
tablet>sustained
release tablet
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• Pharmaceutical excipients.
• Product storage condition.
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REFERENCE:
• TEXTBOOK OF BIOPHARMACEUTICS AND
PHARMACOKINETICS,BY D.M.BRAHMANKAR And
SUNIL .B. JAISWAL,
PG.NO.5-97.
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•Thank you.
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