PHARMACOLOGY IS CHALLENGING SUBJECT TO TEACH AND UNDERSTAND ALSO .....THEIR INTERESTING PART IS TO LEARN ABOUT PHARMACODYNAMICS

1. BY
ASAWETEJASWINI L
DEPARTMENTOF PHARMACOLOGY
ASSIASTANT PROFESSOR
SIDHHIS INSTITUTEOF PHARMACY
THANE

2.  Pharmacodynamics is the study of the
response of the body to the drug.
 Pharmacodynamics is affected by receptor
binding and sensitivity , post receptor effects
and chemical interaction.
 Disorders that affect pharmacodynamics
response include genetic mutation,
malnutrition, , Parkinson's disease and some
forms insulin resistance diabetes mellitus.

3.  A drug may produce its effects through various
mechanism:
 A- Physical mechanism –
 When drug does not produce chemical reaction or
change in body cell and the effect is only physical is
called physical mechanism.
 These includes:
 1.Local application-drugs are applied on the external
surface of skin.
 counter irritant used to mask the pain sensation.
 2.Antacid- antacids are drug used which neutralize
the acid in stomach
 3.Liquid paraffin – it is used to relieve constipation .
 4.Astringents - able to stop a cut from bleeding.
 5.Activated charcoal- Activated charcoal used
to neutralize various poison .

4.  B) Chemical Mechanism –
 In Chemical Mechanism drug acts by
producing chemical reactions in the
body.
 These includes :
 1.Chemically acting antacids –
 Chemically acting antacids react
chemically with HCL of stomach ,
causing neutralization.
 2.Chelating agent –
 Chelating agents are the drug used to
treat poisoning with various metal.

5.  C) Drug Receptor Interaction –
 There are 3 forms of binding to receptors
 1.Agonist
 2.Antagonist
 3.Partial Agonist
 1.Agonist –
 Most of drug bind to receptor and produces maximum
effect is called agonist.
 2.Antagonist –
 The drug work in the opposite to agonist is called
antagonist.
 Antagonist can only produce effect by blocking access of
neurotransmitter (agonist) to the receptor.
 3.Partial Agonist
 A drug which bind and less than maximal effect is called
partial agonist.

6.  Receptors are macromolecules, proteins in
nature which are target sites of drug.
 Drugs have to bind receptors to produce effect.
 Receptors are located mostly on the cell
membrane
 Types of Receptor –
 1. Ion Channel Receptors
 2.G- Protein Linked Receptor
 3.Enzyme Receptor
 4.Nuclear Receptor

7.  1.Ion Channel Receptors –
 These receptors have a channel through ions
can move inside and outside the cells.
 They are located on the cell surface.
 They enclose ion selective channels for
sodium , potassium , calcium and chloride.
 When an agonist is bound to these receptors
they convey signals.
 E.g. Muscarinic , Noradrenergic receptor

8. These are largest class of receptors.
 They are located on the cell membrane.
 G- Protein is a connecting link between
receptor and effectors system like
enzymes , carrier molecules etc
 They link with GTP (guanosine
triphosphate) and GDP (Guanosine
diphosphate)
 It is used as a source of energy for
protein synthesis and gluconeogenesis.

9.  3.Enzyme receptor –
 These receptors are cytoplasmic receptors.
 Their action involves enzymatic activation by
phosphorylation.
 Phosphorylation is the addition of a phosphoryl
(PO3) group to a molecule.
 Ex. Insulin receptor, Cytokine receptor
 Cytokine receptor are cell-surface glycoprotein's
bind specifically to cytokines and transduce their
signals.
 The receptor for insulin is a large protein that binds
to insulin and passes its message into the cell.
 4.Nuclear receptor –
 Present either in cytoplasm or nucleus of the cell.
 Vit A, corticosteroids etc act through these response
receptors.

10.  When two or more drugs are given
simultaneously or directly after each .
 There are different types of effects
produced when two or more drugs are
combined.
 1.No interference with each others effects.
 2.May oppose each others action
(antagonism)
 3. May produce similar actions on the same
organ(synergism ).

11.  Following factor influencing the drug
response
 1. Drugs factor –
 Physical properties of drug such physical
state, crystal structure, size of particles of
drug determines the ability of absorption
and drug effect.
 Drug and dosage form such as solid , liquid
and semisolid. Small dose may show less
effect and high dose may cause
unconsciousness , coma or death.
 Repeated administration of drug produce
tolerance .

12.  Age-The adult dose is for people between 18-
60 years of age.
 The tissue of infant and child are highly
sensitive to large number of drug.
 Geriatric age group (above 60 yr) requires
special consideration like reduced body weight ,
reduced body fat, reduced renal and hepatic
function .
 Body weight – dose is given per kg body weight.
 Allergy – may cause skin rashes , fall of BP.
 Food- drugs are better absorbed in empty
stomach.
 To prevent gastric irritation most drugs taken
after or between foods.

13. (A)Liver Diseases cause individual variation in drug response
– ↓ Plasma protein binding for warfarin, tolbutamide → leads adverse effects.
– ↓ Hepatic blood flow → ↓ clearance of morphine-propanolol may affected
– Damage liver microsomal enzymes may lead to toxic level of Diazepam-
rifampicin-theophylline.
(B) Renal Disease
– ↓GFR.
– ↓tubular function.
– ↓Plasma albumin
↓excretion of digoxin-lithium-gentamycin-penicillin.
(C) Malnutrition
– ↓plasma protein binding of drugs.
– ↓amount of microsomal enzymes.
– ↑Increases portion of free, unbound drug
e.g. warfarin

14.  Genetic abnormality influence the dose of drug
and response to drugs.
 Idiosyncrasy –
 Idiosyncrasy is abnormal genetic response to
the drug .
 It is usually harmful.
 These type of response seen in small portion of
population.
 Ex. Aplastic anaemia (bone marrow cannot
make enough new blood cells ) due to
chloramphenicol antibiotic used in typhoid and
cholera.

15.  Routes of administration –
Some drugs are incompletely absorbed after oral
intake , when given intravenously.
 Time of administration-
Hypnotic acts better when administered at night and
smaller doses are required.
 Effect of climate –
Metabolism of drug is low in hot and humid climate
Purgative acts better in summer while diuretics act
better in winters.
 Preparation of drug
Drugs in solid forms disintegrate slowly .onset of
action is rapid when drug is given in liquid form