Nomenclature:
Every drug has three names:
1) Chemical Name:
 The drug is named according to its chemical
structure.
2) Generic name (common name):
 Non proprietary name is assigned to the drug to
be easy to remember.
 It should reflect some important pharmacologic
or chemical characteristics of the drugs.
3) Brand name (trade name):
 Proprietary name is privately owned by the
manufacturer to distinguish certain drug product
from the other.
 The
name may have an indication to its
therapeutic use or the name of the manufacture.
e.g. Aspirin
Chemical name:
Acetyl salicylic acid
Generic name:
Aspirin
Brand name:
Rivo
Aspocid
Juspirin
Alexoprin
e.g. Acetaminophen
Chemical name:
N-acetyl-p-amino phenol
Generic name:
Acetaminophen (USP) or
Paracetamol (BP)
Brand name:
Abimol
Paramol
Panadol
e.g. Ketoprofen
Chemical name
2-(3-benzoylphenyl)
propanoic acid
Generic name:
Ketoprofen
Brand name:
Ketofan
Alcofan
Profenid
Pharmacodynamics
How do drugs act?
Drugs can produce their effects through one or
more of the following mechanisms.
1) Drug-receptor interactions:
 The cells in certain tissue contain structures
called receptors.
 Receptors are macromolecules component of
the cell that bind the drug to produce a
response.
 Receptors are located at cell membranes or in
the cell nucleus.
The drug is thought to fit onto
a receptor like a key fits a lock.
The ability of the drug to bind
to the receptor depends on the
bond formed between the drug
and the receptor.
[D] + [R]
[DR]
Response
Agonist:
A drug which can bind to a
receptor
to
produce
a
response.
Antagonist:
A drug which bind to receptor
and
produce
no
effect
(compete with the agonist and
inhibit its effect).
2) Antimetabolites/cytotoxic:
 Drug act by impairing cell reproduction.
 This means that the affected cells may remain
alive and may continue to carry out many of their
functions,
but
are
unable
to
reproduce
successfully, leading to cell death (Methotrxate,
Cyclophosphamide).
 The drug may resemble substances which are used
by the cells for nutrition and when absorbed, the
cells can not used them and so failed to multiply.
 The sulphonamides which are used to stop the
multiplication of bacteria are good example.
 They are very similar in structure to para-
aminobenzoic acid and certain bacteria can not
distinguish
between
them
and
sulphonamides and stop generation.
absorb
the
3) Action on enzymes:
 Enzymes are substances which speed up many
chemical processes within the body.
 Drugs
may
produce
their
effects
through
inhibition or stimulation of certain enzymes.
 Sulphonamides are used as antibacterial agents as
they inhibit folate synthase enzyme so decrease
the synthesis of folic acid by bacteria
death
4) Action on cell membrane:
 The action of nerves and muscles depends on ions
passing across the membranes surrounding these
cells.
 Certain drugs interfere with the movement of
these ions and thus prevent nerve or muscle
function (local anaesthetics).
5) Chelating agents:
 Adsorb
drugs,
substances
in
electrolytes
the
or
intestine to
biological
form
non-
absorbable complex that is excreted in the feces
(Cholestyramine).
 Activated charcoal is used as a non-specific
antidote in treatment of poisoning as it adsorbs
poisons
on
its
surface
absorption from the GIT.
and
inhibit
their
Pharmacokinetics
I.
Drug Absorption
II. Drug Distribution
III. Drug Metabolism
IV. Drug Excretion
These factors determine
the
drug
dose
frequency
administration
and
of
I. Drug Absorption
Absorption is the transport
of drug from the site of
administration to the blood
stream.
Drugs must be librated and
dissolved before it can be
absorbed
into
systemic
circulation.
Absorption
involves
the
passage of the drug across cell
membranes.
II. Drug Distribution
 After the drug reaches the blood
stream, the drug is distributed
through the body fluids and
tissues.
 Drugs exist in two forms: bound
and unbound (free) forms.
 The
protein-bound
drug
is
inactive and not subjected to
metabolism or excretion.
 The binding capacity of plasma protein is limited.
 Once saturation has been reached, a small
increase in drug dose
increase in free drug
concentration
pharmacological activity.
 Competition of drugs for binding to plasma
protein
serious drug interactions.
 Aspirin + Warfarin
Aspirin displaces warfarin from plasma protein
bleeding.