The document discusses drug absorption and factors affecting it. It defines absorption as the movement of an unchanged drug from the site of administration to systemic circulation by crossing biological membranes. The main mechanisms of drug absorption discussed are passive diffusion, carrier-mediated transport, and endocytosis. Pharmaceutical factors that can affect the rate of drug absorption include disintegration time, dissolution time, manufacturing variables like granulation method and compression force, and the type of excipients used in the formulation.

1. Department Of Pharmaceutics,
SREE DATTHA INSTITUTE OF PHARMACY, Sheriguda,
Ibrahimpatnam,Telangana
Presented by: Kiran solanki(16U21R0009)
Under the guidance of: Assistant Professor Mrs. Naga Chandrika
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2. 1. Introduction to drug absorption
2. Mechanism of drug absorption
3. Pharmaceutical factors affecting the rate of drug absorption
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3. Absorption:
• Definition:
The process of movement of unchanged drug from the site of administration to
systemic circulation(Blood steam) by crossing biological membrane.
• For example:
If the drug is administered through:
Oral route: from stomach and intestine to portal circulation
Rectal route: from rectum to system circulation
Intramuscular route: from muscles to systemic circulation
No absorption is needed if given intravenously
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4. Pharmacokinetic parameters:
1. AUC (Area Under the Curve)
2. Cmax (Peak plasma drug concentration)
3. Tmax (Time of peak plasma drug)
Pharmacodynamic parameters
1. Minimum Effective Concentration (MEC) /
Minimum Inhibitory Concentration (MIC)
2. Maximum Safe Concentration (MSC) /
Maximum Safe Dose (MSD)
3. Duration of action
4. Onset time
5. Intensity of action (Peak response)
6.Therapeutic Range (Therapeutic window)Plasma concentration curve
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6. 1. Passive diffusion
2. Pore transport
3. Carrier-mediated transport:
i. Facilitated diffusion
ii. Active transport
4. Ionic or electrochemical transport
5. Ion pair transport
6. Endocytosis
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7. • Also known as non-ionic diffusion.
• Passive transport is a process by which an ion or
molecule passes through a cell wall via a concentration
gradient, or from an area of high concentration to an
area of low concentration.
• Absorption of 90% of drugs.
• The driving force for this process is the concentration or
electrochemical gradient.
• Passive diffusion is best expressed by Fick’s first law of
diffusion which states that the drug molecules diffuse
from a region of higher concentration to one of lower
concentration until equilibrium is attained & the rate of
diffusion is directly proportional to the concentration
gradient across the membrane.
Where, dQ/dt = rate of drug diffusion
D = diffusion coefficient of drug through the
membrane
A = surface area of the membrane through
which drug diffusion is taking place
Km/w = partition coefficient of the drug between
the lipoidal membrane and GI fluids
CGIT = concentration in GIT
Cp = concentration in plasma
T = thickness of the membrane
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T

8. 1. Downhill transport.
2. Greater the surface area & lesser the thickness of the membrane,
faster the diffusion.
3. Equilibrium is attained when the concentration on either side of the
membrane become equal.
4. Greater the membrane/ water partition coefficient of drug, faster the
absorption.
5. The unionized species are 3-4 times more faster transported
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9. • Important in the absorption of low mol. wt., low mol. size & generally
water-soluble drugs
• e.g. urea, water & sugars.
• The driving force for the passage of the drugs is the hydrostatic or the
osmotic pressure
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10. • It Involves a carrier which binds reversibly with the solute molecules to
be transported to yield the carrier solute complex which transverses
across the membrane to the other side where it dissociates to yield the
solute molecule
• The carrier then returns to its original site to accept a fresh molecule of
solute.
• There are two types of carrier mediated transport system:
a) facilitated diffusion
b) active transport
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11. i. Facilitated diffusion
• In this process concentration
gradient itself act as driving force.
• In this system, no expenditure of
energy is involved (down-hill
transport), therefore the process is
not inhibited by metabolic poisons
that interfere with energy
production.
ii. Active transport
• The driving force is against the concentration gradient or
uphill transport.
• Since the process is uphill, energy is required.
• As the process requires expenditure of energy, it can be
inhibited by metabolic poisons that interfere with energy
production.
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12. • The charge on membrane influences the
permeation of drugs.
• Molecular forms of solutes are unaffected by
the membrane charge & permeate faster
than cationic forms.
• Thus, at a given pH, the rate of permeation
may be as follows:
• Unionized molecule > anions > cations
• Once inside the membrane, the cations are
attached to negatively charged intracellular
membrane, thus giving rise to an electrical
gradient.
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13. • It is another mechanism that is able to
explain the absorption of such drugs
which ionize at all pH condition.
• It involves transport of charged molecules
due to the formation of a neutral complex
with another charged molecule carrying
an opposite charge.
• Such neutral complexes have both the
required lipophilicity as well as aqueous
solubility for passive diffusion.
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14. • It involves engulfing extracellular materials within a segment of the cell membrane to form a saccule or a vesicle
(hence also called as corpuscular or vesicular transport) which is then pinched off intracellular.
• Endocytosis includes two types of processes:
1. Phagocytosis
2. Pinocytosis
• A. phagocytosis : This process involves the absorptive uptake of solid particulates, macromolecules
• B. Pinocytosis : This process is important in the absorption of oil soluble vitamins & in the uptake of nutrients.
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15. 1. Disintegration time: it is the time required for a dosage form to break
up in to granules of specified size (or smaller) under carefully specified
conditions
• Disintegration time is directly proportional to amount and binder and
compression force.
• Ex: coated tablets have long disintegration time and fast dispersible
tablets have short disintegration time.
2. Dissolution time: it is the time required for a drug to solubilises in a
given solvent.
3. Manufacturing variable:
i. Method of granulation
ii. Compression force
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16. I. Method of granulation:
• The method of dry granulation can be used to produce tablets that dissolve at a faster
rate.
• Wet granulation has limitations like formation of crystal bridge and sometimes
chemical degradation.
II. Compression force:
• influence the hardness, density, disintegration and dissolution.
• Higher compression force increases the density and hardness of the tablet, decreases
porosity and hence penetrability of the solvent into the tablet and hence slower the
dissolution and absorption.
4. Pharmaceuticals ingredients(excipients/adjuvants):
More the no. of excipients in the dosage form, greater the potential for absorption and
bioavailability problems
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17. • Excipients:
a. Vehicle
b. Diluents
c. Binders
d. Disintegrants
e. Lubricants
f. Suspending agents
g. Surfactants
h. Buffer
i. Colourant
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