1. Introduction to Pharmacology
Course Coordinator
Jamaluddin Shaikh, Ph.D.
School of Pharmacy, University of Nizwa
Lecture-1
September 17, 2011

2. What is Pharmacology? Study of how drugs function inside the body
Composition
Use
Effects

3. What is Drug? Chemical substance
Used in the treatment, cure and diagnosis of diseases

4. Pharmacokinetics and Pharmacodynamics
Pharmacokinetics (PK) : Effects of body on the drugs
Absorption
Distribution
Metabolism
Excretion
Pharmacodynamics (PD): Effects of the drugs on body

5. Bound Free Free Bound ABSORPTION Free Drug EXCRETION Bound Drug
LOCUS OF ACTION
“RECEPTORS”
TISSUE
RESERVOIRS
Bound
Free
Free
Bound
ABSORPTION
Free Drug
EXCRETION
SYSTEMIC
CIRCULATION
Bound Drug
BIOTRANSFORMATION

6. PK vs PD
Dose
Site of action
Plasma Concentration
Effects PK PD

7. How Do Drugs Work? Work by interact with endogenous protein
Some antagonize, block or inhibit endogenous proteins
Some activate endogenous proteins
A few endogenous proteins have unconventional mechanisms of action

8. Receptor Macromolecular endogenous protein
Primarily located on the plasma membrane
It binds the drugs and initiates its effects

9. Ligand Molecules that bind to receptor is called ligand
A ligand may be
Peptides
Neurotransmitters
Hormones
Drugs

10. Drug-Receptor Binding
Drug-receptor interaction produce pharmacological response
Pharmacological response depends on:
Nature of the drug
No. of receptors
Amount of drug at the receptor site

11. Agonist and its Action Chemical binds to a receptor of a cell
Triggers a response by the cell
Can be endogenous or exogenous
Types of agonists
Full agonist
Partial agonist
Inverse agonist

12. Antagonist and its Action
Binds to receptor but produce no biological response
Blocks the agonist mediated effects
Interactions are reversible or irreversible
Can compete with endogenous ligands

13. Agonists vs Antagonist
Receptor
Effect
No Effect

14. How Do Agonist Interacts with Receptors?
Extracellular
Compartment
Unbound Endogenous Activator (Agonist)
Cell Membrane
Inactive Receptor
Intracellular
Compartment

15. How Do Agonist Interact With Receptors?
Extracellular
Compartment
Bound Endogenous Activator (Agonist)
Cell Membrane
Active Receptor
Intracellular
Compartment
Cellular Response

16. How Do Agonist Drugs Produce Cellular Activity
Displaced Endogenous Activator ( Agonist)
Extracellular
Compartment
Bound Agonist of Receptor (Drug)
Cell Membrane
Active Receptor
Intracellular
Compartment
Cellular Response

17. How Do Drugs Work by Antagonizing Receptors?
Displaced Endogenous Activator ( Agonist)
Extracellular
Compartment
Bound Antagonist of Receptor (Drug)
Cell Membrane
Inactive Receptor
Intracellular
Compartment

18. Two Drugs Given Together: Different Effects
Work independently and produce own effects
May produce similar effects
Addition
Synergism
Potentiation
May produce opposite effects
Competitive antagonism
Non-competitive antagonism
Chemical antagonism
Functional or physiological antagonism

19. Competitive Antagonism
Common drug antagonism
Antagonist competes with agonists for same receptors
Pharmacological effects depends on the concentration of either agonists or antagonists
Antagonism may be reversible or irreversible
Reversible: loose binding
Example: antihistamines, β-blocker
Irreversible: covalent bonding
Example: phenoxybenzamine

20. Non-competitive Antagonism
Antagonists and agonists bind to the different sites

21. Competitive vs Non-competitive Antagonism
Antagonist
Antagonist
Agonist
Agonist
Antagonist
Competitive Antagonism
Binds same site
Chemical similarity
Maximum response with increasing dose of agonist
Non-competitive Antagonism
Binds different site
No chemical similarity
Maximum response with increasing dose of agonist

22. Chemical Antagonism
Involves a direct interaction between an agonist and antagonist in such a way that the effect of agonist is lost

23. Physiological Antagonism
A form of antagonism which occurs when two drugs, each tends to oppose or cancel the effects of other