2. DEFINITION
“Absorption is defined as the process of
movement of unchanged drug from the site of
administration to the systemic circulation.”
3.
4. MECHANISM OF DRUG ABSORPTION
1) Passive diffusion and filtration
2) Specialized transport
A) Carrier- mediated transport
i) Facilitated diffusion
ii) Active transport
a) primary active transport
b) secondary active transport
3) Phagocytosis
4) Pinocytosis
5. Passive Diffusion
It is defined as the
difference in the drug
concentration on either
side of the membrane.
Also called nonionic
diffusion
It is the major process for
absorption of more than
90% of the drugs.
The driving force for
this process is the
‘concentration or
electrochemical gradient’.
6. PORE TRANSPORT
It is also called as Convective transport, Bulk flow
or filtration.
The driving force for this process is the
‘hydrostatic pressure or the osmotic differences
across the membrane’.
The process is important in the absorption of low
molecular weight, low molecular size drugs.
Example: Urea, Water, Sugar
7. CARRIER-MEDIATED TRANSPORT
The mechanism is thought to involve a
component of the membrane called as the carrier
that binds reversibly or non-covalently with the
solute molecules to be transported.
The carrier may be an enzyme or some other
component of the membrane.
Two types
Facilitated diffusion
Active transport
8. FACILITATED DIFFUSION
This mechanism involves
the driving force is
concentration gradient.
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.
9. ACTIVE TRANSPORT
It is process where the
materials are transported
across membranes against
a concentration gradient.
The drug is transported
from a region of lower to
one of higher concentration
i.e.. against the
concentration gradient or
‘uphill transport’.
Examples : Sodium,
potassium, iron, glucose
and vitamins like niacin,
pyridoxine and ascorbic
acid.
10. ENDOCYTOSIS
Also called Corpuscular or Vesicular transport
It involves engulfing extracellular materials within a
segment of the cell membrane to form a saccule
or a vesicle which is then pinched-off
intracellularly.
Includes two type of process:
Phagocytosis and Pinocytosis