The document summarizes key concepts in pharmacodynamics, including: 1. The major mechanisms of drug action include stimulation, depression, irritation, replacement, and cytotoxic effects. Drugs primarily act by interacting with biomolecules like enzymes, ion channels, transporters, and receptors. 2. Receptors can be intracellular or extracellular, and the major receptor types are G-protein coupled receptors and ion channel receptors. G-protein coupled receptors activate downstream effector pathways upon ligand binding like the cAMP pathway and IP3-DAG pathway. 3. Mechanisms of drug action are explained at the molecular level, with examples of how drugs can inhibit or activate enzymes and examples of different receptor types.

1. Assignment on
PHARMACODYNAMICS
SUBMITTED BY : Anjali kumari
PHARM. D 2ND YEAR
ROLL NO. 03
SUBMITTED TO :RANJEET
KUMAR (Department of
PHARMACOLOGY)

2. PHARMACODYNAMICS
“WHAT THE DRUG DOES TO THE BODY”
• Principle of drug action:
1. Stimulation: selective enhancement of level of activity of specialized cells.
Ex. Adrenaline – stimulates heart.
2. Depression: selective reduction in activity of specialized cells.
Ex. Barbiturates – depresses CNS

3. 3.Irritation- Non- selective, often noxious effect.
Ex. Senna-constipation
4.Replacement- Therapy involving supply of natural metabolites or hormone
which are lacking in body.
Ex. Insulin in diabetes.
5.Cytotoxic action- Selective cytotoxic action on invading parasites or
cancer cells attenuating them.
Ex. Penicillin

4. MECHANISM OF DRUG ACTION
• Majority of drugs produce their affect by interacting with a discrete target
biomolecule which is usually protein.
• These proteins can be grouped into four categories:
1. ENZYME:
- Drugs can either decrease or increase enzymatically mediated reactions.
“ENZYME-SUBSTRATE COMPLEX FORMED”

5. Enzyme inhibition: selective inhibition of particular enzyme.
1. Competitive inhibition
2. Non-competitive inhibition

6. 2. ION CHANNELS:
• Ligand gated ion channel
• G-protein regulated ion channel
• Voltage gated ion channel

7. 3.TRANSPORTERS-
Movement of substrate across membrane with the help of specific carriers called
transporters.

8. 4.RECEPTORS:
-Macromolecule or binding sites located on surface or inside the
surface of cell
Serves to recognize the signal molecule /drug and initiate the
response to it.
• LIGANDS- Any molecules that attaches selectively to particular receptor or sites.

9. RECEPTORS-
• INTRACELLULAR RECEPTORS
• EXTRACELLULAR RECEPTORS
INTRACELLULAR EXTRACELLULAR
Receptors located inside the cell
surface.
Receptors located on cell surface.
Ligands that binds to intracellular
receptor are smaller in size.
Ligands that binds to extracellular
receptors are larger in size.
Hydrophobic Hydrophilic
Ex. Steroid hormones Ex. GPCR

10. RECEPTORS(TRANSDUCER MECHANISM):
-The transducer mechanisms can be grouped into following 5 categories:
1. G-protein coupled receptor
2. Ion-channel receptors
3.Trans membrane enzyme linked receptors
4.Trans membrane JAK-SAT binding receptors
5.Receptors regulating gene expression

11. GPCR:
• G-protein coupled receptor
• Serpentine receptor
• 7-pass receptor
• Polar, charged, high molecular weight

12. G-proteins are trimeric proteins (consists of alpha, beta and gamma subunits)
In inactive state GDP is bound to alpha subunit
Activation through receptor leads to displacement of GDP by GTP
The activated alpha subunit carrying GTP dissociates from other two
subunits
Either activates or inhibits the effector
The beta and gamma subunits activates receptor operated k+ channels

13. IMPORTANT G- PROTEINS:
• Gs : Adenylyl cyclase activation, Ca+2 channel opening
• Gi : Adenylyl cyclase inhibition, k+ channel opening
• Go : Ca+2 channel inhibition
• Gq : Phospholipase C activation
There are three major effector pathways
through GPCR functions:
1. Adenylyl cyclase : c AMP pathway
2. Phospholipase C : IP3 –DAG pathway
3. Channel regulation

14. 1.Adenylyl cyclase: c AMP pathway

16. 2.Phospholipase C: IP3- DAG Pathway