1. 1
Topic name : Gastrointestinal absorption
and role of dosage forms in absorption of
drugs.
Student name :- Mr. Gaurav
Anil Patil
M pharm 1st Year
Pharmaceutics Department

2. Index
o Introduction
o Mechanism of absorption
o Role of different dosage forms in absorption of drugs
• Solution
• Suspension
• Capsules
• Tablets
o Reference
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3.  Absorption
o The movement of unchanged drug from the site of
administration to the systemic circulation is called as
absorption.
Or
o The transportation of the unmetabolized drug from the site
of administration to the body circulation system.
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4. Mechanism of absorption
There are three broad categories are :
 Transcellular/intracellular transport
Passive Transport Processes
A. Passive diffusion
B. Pore transport
C. Ion-pair transport
D. Facilitated diffusion
Active transport processes
A. Primary
B. Secondary
a. Symport (Co-transport)
b. Antiport (Counter transport) 4

5.  Para cellular / Intercellular Transport
 Endocytosis
A. Pinocytosis
B. Phagocytosis
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6.  Steps involved in absorption of different dosage
forms
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7.  Role of dosage form in drug
absorption
Conventional dosage forms may be broadly characterized
as:
• Solutions
• Suspension
• Capsules
• Tablets
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8.  Solution
• Solutions such as syrups and elixirs show fast and often
complete absorption of drug because they do not have
dissolution problem.
• The factors that affect drug absorption from solution
include:
• Viscosity(Absorption rate decreases with increasing viscosity because the
slower rate of movement of drug molecules to the absorbing
membranes.)
• Solubilizes
• Stabilizers
• Stability
• The vehicle used in syrups, elixirs and emulsions may be
aqueous or non-aqueous(e.g., PEG, PG, alcohol) or non-
water miscible(e.g.. vegetable oils). 8

9. • The rate of drug absorption from non-aqueous or non-
water miscible vehicle based solution is less than the rate
of drug absorption from water based solution.
• The selection of vehicle for solution dosage form depends
on the physiochemical properties of the drug such as
• Solubility
• Partition Coefficient
• Ionization
• Hydrogen Bonding
• Surface activity
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10. • For example
solution of paracetamol is prepared with PEG 400 as it is sparingly
soluble in water. Certain materials such as sorbitol or hydrophilic
polymers are added to a solution dosage form, to improve pourability
and palatability by increasing the viscosity of the preparation
• Due to good systemic availability, solutions are frequently
used as bioavailability standards.
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11.  Suspension
Suspension
Fine particle
Dissolution
Solution
Absorption
.
o The factors that affect drug absorption from suspension
includes:
• Particle size
• Polymorphism 11

12. • Wetting agents
• Viscosity of the medium
• Suspending agents
• Drug in a suspension is in the solid form, but is finely
divided and has a large surface area.
• Weating agents present in the suspension helps in easy
penetration of drug into the absorption surface.
• Finally divided solid particles in suspension are stabilized
with suspending agents. Suspending agents retard
sedimentation of dispersed particles in suspension.
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13. 13
o Suspending agent may increase the viscosity of drug
vehicle and may decrease the rate of drug dissolution
which affect the absorption of the drug.
o For Example:
The blood levels of trimethoprim and
sulfamethoxazole were compared in 24 healthy subjects
following oral administration of 3 forms. The
absorption rate of each drug was significantly greater
with the suspension this with the tablet or capsule.

14.  Capsule
o Factors affecting the absorption :
• Drug particle size
• Dissolution rate
• Polymorphism
• Excipients
• Interactions
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15. o In capsule ,on disruption of the shell the encapsulated
powder/granules mass should disperse rapidly to expose a
large surface area in the gastrointestinal fluids.
o Diluents added to capsules dosage form may affect the
dissolution of filled drug in capsule shell.
o Hydrophilic diluents are added in the capsule for poorly
water soluble drugs ,they enhance the dispersion rate of the
shell.
o drug absorption from capsule may also be affected by
particle size and chemical and physical incompatibility of
the drug with its excipients.
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16.  Tablet
o There are various types of tablet formulations are
present
Compressed tablets>film coated tablets>enteric coated
tablets>sustained release tablet
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17. o Factors that affect the absorption of tablet
• Effective surface area
• Dissolution
• Permeability
• API and excipients
o Most formulations require the incorporation of
hydrophobic lubricants, such as magnesium stearate, to
produce an acceptable tablet.
o Larger the quantity of lubricant in a formulation the
slower is the dissolution rate.
o Compression force may also be an important factor in
drug bioavailability from compressed tablets.
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18. THANK
YOU
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