Pharmacology and Toxicology
(Pharmacokinetics)
By - Devendra kumar Rawat
Assistant Professor
M.Pharm (Pharmacology)
B.M.S. College of Pharmacy, Nasratpur, Tiloi, Distt.-Amethi
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Pharmacokinetics
Pharmacokinetics is the quantitative study of drug movement
in, through and out of the body.
The intensity of response of drug is depends on the
pharmacokinetic properties of drug.
It deals with the ADME –
 Absorption,
 Distribution,
 Metabolism and
 Excretion of drugs
Absorption & Distribution are influenced by the formulation.
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Devendra Kumar Rawat

Pharmacokinetics
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Schematic depiction of pharmacokinetic process

Pharmacokinetics
 Absorption :
 Absorption is movement of the drug from its site of
administration into the circulation.
 The drug molecules in their transfer from the site of
administration to the blood have to cross a complex biological
barrier composed of lipids, proteins, lipo – proteins,
polysaccharides, etc.
 This barrier is semi permeable biological membrane.
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Biological membrane
This is a bilayer (about 100 Å
thick) of phospholipids and
Cholesterol molecules.
oHead end – Hydrophilic
(water loving)
oTail end – Hydrophobic
(water hating or lipid loving)
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Biological membrane
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Pharmacokinetics
 Absorption
 Mechanism of drug absorption :
 The drugs can pass through cell membrane by two processes,
they are -
I. Passive transfer
i. Simple diffusion
ii. Filtration
II. Specialized transfer
i. Active transport
ii. Facilitated diffusion
iii. Pinocytosis
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Pharmacokinetics
Difference between Passive transport & Active Transport
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Particulars Passive Transport Active Transport
Concentration Gradient From Higher
concentration to lower
concentration
From lower concentration
to higher concentration
Carrier No need of carrier Needs carrier
Energy No energy required Energy required as ATP
Efficiency of the process It is a slow process It is a rapid process
Directionality Bidirectional process Occurs in one direction

Pharmacokinetics
 Absorption
I. Passive transfer : This
process does not require any
energy.
i. Simple diffusion :
 The drug diffuses across
the membrane in the
direction of its
concentration gradient i.e.
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Devendra Kumar Rawat
High Low

Pharmacokinetics
 Absorption
i. Simple diffusion :
 Water soluble drug
(ionized or polar) is readily
absorbed via aqueous
channels or pores in cell
membrane.
 Lipid soluble drugs ( non
ionized or non polar) is
readily absorbed via cell
membrane itself.
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Devendra Kumar Rawat

Pharmacokinetics
 Absorption
ii. Filtration :
 Filtration is passage of
drugs through aqueous
pores in the membrane or
through paracellular spaces.
 Lipid insoluble drugs cross
biological membranes by
filtration if their molecular
size is smaller than the
diameter of the pores.
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Devendra Kumar Rawat

Pharmacokinetics
 Absorption
II. Specialized transport :
 It requires energy.
i. Active transport
 It is a selective process
which requires energy in the
form of Adenosine
triphosphate (ATP).
 It also requires a carrier to
transfer drug, so is also
called “carrier transport”.
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Low High

Pharmacokinetics
 Absorption
II. Specialized transport :
ii. Facilitated diffusion
 It is similar to carrier
transport but it does not
require energy.
 Carriers used in this
diffusion are solute carrier
transporter (SLC), moves
poorly diffusible substrates.
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High Low

Pharmacokinetics
 Absorption
II. Specialized transport :
iii. Pinocytosis
 It is the process of transport
across the cell by formation
of vesicles.
 Proteins and
macromolecules are
transported by this process.
 In this cells engulf the
macromolecules from ECF.
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