pharmacology,general pharmacology,pharmacokinectics,absorption of drugs,absorption

1. D R . I . S H E I K N A S A R
A S S O C I A T E P R O F E S S O R
D E P A R T M E N T O F P H A R M A C O L O G Y
ABSORPTION OF
DRUG

2. ABSORPTION OF DRUG
PHARMACOKINETIC -the branch of pharmacology
that studies the fate of pharmacological substances
in the body, as their
 absorption,
 distribution,
 metabolism,
 and elimination.
DRUG ABSORPTION is a pharmacokinetic
parameter that refers to the way a drug is absorbed
from a pharmaceutical formulation into the
bloodstream.

3. ABSORPTION is the process by which drug
molecules gain access to the bloodstream
from the site of drug administration.
The speed of this process (THE RATE OF
DRUG ABSORPTION) and its completeness
(THE EXTENT OF DRUG ABSORPTION)
depend on the route of administration.

4. METHODS OF DRUG ABSORPTION
I. PASSIVE DIFFUSION
II. FACILITATED PASSIVE DIFFUSION
III. ACTIVE TRANSPORT
IV. PINOCYTOSIS

5. I.PASSIVE DIFFUSION
Drugs diffuse across a cell membrane from a region
of high concentration (eg, GI fluids) to one of low
concentration (eg, blood).
Diffusion rate is directly proportional to the
concentration gradient but also depends on the
molecule’s
lipid solubility,
 size,
degree of ionization,
 the area of absorptive surface.

6. II.FACILITATED PASSIVE DIFFUSION
 Certain molecules with low lipid solubility (eg, glucose)
penetrate membranes more rapidly than expected.
 A carrier molecule in the membrane combines reversibly
with the substrate molecule outside the cell membrane,
and the carrier-substrate complex diffuses rapidly across
the membrane, releasing the substrate at the interior
surface.
 In such cases, the membrane transports only substrates
with a relatively specific molecular configuration, and the
availability of carriers limits the process.
 The process does not require energy expenditure, and
transport against a concentration gradient cannot occur.

7. III.ACTIVE TRANSPORT
 Active transport requires specific carries and
ATP.
The specific carrier protein carry the drugs that
closerly resemble the structure of the naturally
occurring metabolites specific for the carrier.
 It is capable of transporting from low to high
concentration compartments.

8. IV.PINOCYTOSIS
In Pinocytosis, fluid or particles are engulfed by a
cell.
Pinocytosis probably plays a small role in drug
transport, except for protein drugs.
Endocytosis is the process of capturing a
substance or particle from outside the cell by
engulfing it with the cell membrane, and bringing
it into the cell.
Exocytosis describes the process of vesicles fusing
with the plasma membrane and releasing their
contents to the outside of the cell.

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