Pharmacodynamics

1. Presented by: Ravi Kumar
M.Pharmacy 1st Semester
Department of pharmacology
G.H.G Khalsa college of Pharmacy

2. Mechanism of drug action-
• the specific biochemical interaction through which a
drug substance produces its pharmacological effect
• A mechanism of action usually includes mention of
the specific molecular targets to which the drug
binds, such as an enzyme or receptor
Pharmacodynamics:
 Effects of drugs and the mechanism of their action
 What does a drug do and how does it do it

3. Mechanism of drug action-
 study of drug effects
 modification of one drug‘s action by another
Drugs acts in four different levels
1. molecular
2. Cellular
3. tissue
4. system

4.  Hormones &neurotransmitter receptors
 Enzymes
 Carrier molecules
 Ion channels [ligand gated or voltage operated]
 Idiosyncratic targets such as metal ion, surfactant
protein etc.
 Nucleic acid

6.  The molecular selectivity of drug action
Determine the similarity or divergence of structure of
different molecular targets
 The tissue selectivity of drug responses
In accordance with the distribution of the molecular
target throughout the body
 The rapidity &persistence of the menifestation of
cellular & tissue responses

7.  A protein molecular target for a drug
 The largest number of drug act through them control
effectors
 Endogenous substances & drug
 Regulate cell function by altering
 Enzyme activity
 Permeability to ions
 Conformational features
 Genetic material

9.  Receptor: it is defined as a macromolecule or binding
site located on the surface or inside the effector cell that
serves to recognize the signal molecule and initiate the
response to it but itself has no other function.
 The following terms are used in describing drug
receptor interaction
 Agonist
 Inverse agonist
 Antagonist
 Partial agonist
 Ligand

10.  Protein in nature
 Molecular weight 45-200kda
 Subunits, subtype depending on tissue
 Saturable
 Can be up & down regulated etc.

11.  Ligand gated ion channel
 G-protein coupled receptors
 Enzyme linked receptor
 Nuclear receptors
Ion channel
 Localised on the cell membrane.
 Coupled directly to an ion channel.
 It is a channel with a receptor site.
 Agonists open the channel.

12.  Antagonists prevent agonist from opening the channel
 Inverse agonist closes an open channel
 Channel properties are determined by the composition
of subunit isoforms
1. Agonist affinity
2. Ion permeability
3. Conductane properties
4. Activation and deactivation times
5. Desensitisation kinetics
 Activity can be regulated by varying composition of
different subunits

13. Two main families
1. Nicotinic receptor family (include nACh receptors,
GABAA, GABAC,glycine receptors and the 5-HT3
receptors)
2. Glutamate receptor family(several different receptor
classified into NMDA receptor and non NMDA
receptors)

14.  G-protein coupled receptor, also called seven
transmembrane receptor or heptahelical receptor,
located in the cell membrane that binds extracellular
substances to an intracellular molecule called a G-
protein(guanine nucleotide binding protein)
 G protein coupled receptors are found only in
eukaryotes, including yeast and animals
 The ligand that bind and activate these receptors
include light sensitive compounds, odors, hormones
and neurotransmitters, and vary in size from small
molecule to peptide to large protein

16. There are two principal signal transduction pathway
involving the G-protein coupled receptors:
1. The CAMP signal pathway: the CAMP dependent
pathway,so known as the adenylyl cyclase, is G
protein coupled receptor triggered signaling cascade
used in cell communication.
2. The phosphatidylinositol signal pathway:
phosphatidylinositol 4,5-bisphosphate is an essential
lipid involved in metabolic processes. It is integral to
the cell membrane of all animal and plant cells and
acts as a second messenger in a variety of signaling
pathway

18.  Nuclear receptors are a class of proteins found within cells that
are responsible for sensing steroid and thyroid hormones and
certain other molecules.
 Nuclear receptor have the ability to directly bind to DNA.
hence these receptors are classified as transcription factors.
 Receptors is directly interact with and control the expression
of genomic DNA.