This document discusses gastrointestinal absorption and the role of different dosage forms in drug absorption. It begins by defining absorption and describing the main mechanisms of absorption, including transcellular transport processes like passive and active transport, as well as para cellular and endocytic transport. It then examines how various dosage forms like solutions, suspensions, capsules and tablets can impact drug absorption based on factors like viscosity, particle size, dissolution rate, and presence of excipients. Solutions provide fast and complete absorption while other forms depend on dissolution and may be affected by things like viscosity, particle size, and interactions with excipients in the dosage form.

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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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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