1. INTRODUCTION to Pharmacology

2. What is pharmacology?
It is the study of the actions, mechanisms, uses, and adverse effects of drugs
A Drug is any natural or synthetic substance that alter the physiologic state of a living organism

3. Drugs are divided into:
Medicinal drugs:
These are used in the prevention, treatment and diagnosis of disease
Non-medicinal drugs or social drugs:
These are used for purposes other than treatment e.g. illegal mood- altering substances such as cannabis, heroin and cocaine

4. Drugs name and classification
Factors that are used to classify drugs:
Pharmacotherapeutic action
Pharmacologic action
Molecular action
Chemical nature

5. Definitions Pharmacodynamics:
It is what the drug do to the body i.e. drug actions on the receptor, tissue, organ or system.
Pharmacokinetics:
It is what the body to the drug i.e. absorption, distribution, metabolism and elimination

6. Pharmacodynamics

7. Targets of drugs Receptors Enzymes Ion channels Carrier molecules
Physical or Chemical

8. Drug receptors Highly specific, highly sensitive binding site
Found on the surface of the cell membrane, enzyme molecules on nuclear membranes.

9. Receptor Specificity
There are a number of specific ligands and a number of associate receptors
Affinity
The extent to which the ligand is capable of binding and remains bound to a receptor
High affinity: The ligand bind well and remains bound for long enough to activate the receptor
Low Affinity: The ligand binds less well and may not remain bound long enough to activate the receptor

10. The receptor intrinsic activity
The extent to which the ligand activates the receptor
High intrinsic activity: the ligand produces a large effect on the post synaptic cell
Low intrinsic activity: the ligand produces a small or inconsistent effect on the post synaptic cell

11. Classes of Ligands Agonists High affinity High intrinsic activity
Antagonist
Low intrinsic activity

12. Agonists
An agonist is a drug that binds to a receptor and activates it to give a response
There are 2 types of agonists:
Full agonist: is a drug when bound to a receptor produces 100% of the maximum possible biologic response
Partial agonist: a drug that produce less than 100% of the maximum possible biologic response no matter how high their concentration

13. Antagonist
An antagonist is a drug that bind to a receptor and produce no response.
Type of drug antagonism:
Receptor antagonists
Competitive: the antagonists competes with the agonist at the same receptor site of an agonist and binds to it reversibly. By increasing the concentration of drug agonist the antagonism is abolished. E.g. antihistamine competes with histamine at its receptor site

14. Non competitive: the antagonist binds irreversibly to a different site on the enzyme e.g. than the agonist, noncompetitive agonists can not overcome by increasing the concentration of the drug agonist. E.g. succinylcholine is irreversible neuromuscular blocker.

15. AGONIST R R+
RESPONSE
Resting state
Activated state
-ve
-ve
ANTAGONIST

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Physiological antagonism: e.g. glucagon and insulin. Histamine and epinephrine
Chemical antagonist: is the type of a drug that acts by binding chemically to the compounds and inactivates it. E.g. chelating agents, charcoal (poisoning with iron)
Pharmacokinetic antagonist: by increasing the metabolism and excretion of a drug, e.g. enzyme induction to speed metabolism

17. Dose- response curve
The response to increasing doses of an agonist or antagonist are plotted graphically.
It can measure the following:
Efficacy: is the maximum effect (Emax) which can be obtained from a large dose of the drug.
Potency: is the amount (dose) of drug or concentration in the plasma that can produce a similar effect by a dose of another drug

18. EC50 (Effective concentration): is the concentration that produce 50% of the maximum effect.
ED50 (Effective dose): is the dose that produces the response of 50% of subjects
LD50 (Lethal dose): is the dose that cause death in 50% of subjects

19. Non competitive antagonist will bind irreversibly with the receptor leading to decrease in number of receptors available for binding with the agonist
This will cause the maximum effect of the agonist to be less than when it is used alone or with competitive antagonist

22. Therapeutic index
Is the ratio between the average maximum tolerated dose LD50 and the average minimal effective dose ED50
TI= LD50/ ED50
It indicates the margin of safety in use of a drug
The higher the TI the safer the drug