Introduction To Pharmacotherapeutics

INTRODUCTION TO
PHARMACOTHERAPEUTICS
Lecture 1
Objectives
 Def. of pharmacology
 History of pharmacology
 Def. of pharmacotherapeutics
 Nature of drugs
 Drug body Interaction
 Pharmacodynamic principles
 Pharmacokinetic principles
What is pharmacology ?
 Pharmacology is the study of substances that interact with

living systems through chemical processes, especially by
binding to regulatory molecules and activating or inhibiting
normal body processes.”
 These substances may be chemicals administered to achieve a
beneficial therapeutic effects on some process within the
patient or for their toxic effects on regulatory processes in
parasites infecting the patient.
Pharmacology: Is the study of interaction between drugs and the
body
Clinical Pharmacology: the science that care about actions and

proper uses of medicines in humans and implements that
knowledge in clinical practice".
Toxicology:. is a scientific discipline, overlapping with biology,
chemistry, pharmacology, and medicine, that involves the study of
the adverse effects of chemical substances on living organisms.
Pharmaco-therapeutic: it deals with drugs/natural products that

interact with the body and used to diagnose, treat, and/or prevent
diseases.
Drugs: are chemicals or natural products that interact with the body.
Pharmacotherapeutics contd.
It includes:
1. Purpose of giving a drug
2. Selection of most appropriate drug
3. Prevent illness
4. Diagnose illness
5. Relieve symptoms
6. Treat and cure illness
Nature of Drugs
 Drug:
 A drug may be defined as any substance that brings about a
change in biologic function through its chemical actions.
 Drug molecule interacts as an Agonist (activator) or Antagonist

(inhibitor) with a specific molecule in the biological system that
plays a regulatory role.
 The component of a cell or organism that interacts with a

drug and initiates a chain of events is called a Receptor.
Drug Characteristics
 Physical nature of drugs
 Drug Size
 Drug Reactivity & drug receptor bond
 Drug shape
 Rational drug Design

Drug - Body Interactions
• The interactions between a drug and the body are
conveniently divided into two classes.
A. Pharmacodynamic process
B. Pharmacokinetic process
Drug - Body Interactions
• Pharmacodynamics: The actions of a drug on the body bring about
certain effects in it which are termed pharmacodynamic effects.
• Pharmacokinetics: The actions of the body on the drug are

called pharmacokinetic effects. These effects are:
• (LADME)
 Libration
 Absorption
 Distribution
 Metabolism
 Elimination
Plasma Site of
Dosage Concen. Action
Effects
Pharmacokinetics Pharmacodynamics
Receptor
• Def: “defined as a macromolecule or binding site

located on the surface or inside the effector cell that
serves to recognize the signal molecule / drug and
initiate the response to it, but itself has no other
function.”
• Receptor Site: “Specific region of the receptor

molecule to which the drug binds”
Effector
• Def: “Component of a system that accomplishes

the biologic system after the receptor is
activated by an agonist; often a channel or
enzyme molecule”
Pharmacodynamic Principles
• Drugs must bind to a receptor to bring about an effect.

• Effects begin from a cellular level
1. Drug(D) + receptor - effector (R) drug-receptor-
effector complex effects
2. D + R drug-receptor complex effector
molecule effect
3. D + R D – R complex activation of coupling
molecule effector molecule effect
4. Inhibition of metabolism of endogenous activator
increased activator increased effect
LOCUS OF ACTION TISSUE
“RECEPTORS” RESERVOIR
Bound Free Free Bound
ABSORPTION Free Drug EXCRETION
SYSTEMIC
Bound Drug CIRCULATION
BIOTRANSFORMATION
Dose Response Relationship
Potency and Efficacy of a Drug
• Potency: Refers to the amount of drug needed to

produce a certain response. A DRC positioned
rightward indicates lower potency.
• Efficacy: Refers to the maximal response that can

be elicited by the drug. The upper limit of DRC is the
index of drug efficacy.
• Note: Efficacy is a more decisive factor in the choice
of a drug.
Potency and Efficacy of a Drug contd
Potency and Efficacy of a Drug contd.
Inferences of previous slide on relative analysis of drugs A, B, C,D.
 Drug A is more potent than drug B, but efficacy of both drugs

is same because maximal response of both drugs is same on
DRC.
 Potency of drug C is more than drug D up to a certain dose.
 Efficacy of drug D is more than drug C because maximal

response of drug D is more than drug C on DRC.
• DRC: Dose Response Curve

• Thank you

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INTRODUCTION TO

 Pharmacology is the study of substances that interact with

Clinical Pharmacology: the science that care about actions and

Pharmaco-therapeutic: it deals with drugs/natural products that

 Drug molecule interacts as an Agonist (activator) or Antagonist

 The component of a cell or organism that interacts with a

 Drug Reactivity & drug receptor bond

 Rational drug Design

• Pharmacokinetics: The actions of the body on the drug are

• Def: “defined as a macromolecule or binding site

• Receptor Site: “Specific region of the receptor

• Def: “Component of a system that accomplishes

• Drugs must bind to a receptor to bring about an effect.

ABSORPTION Free Drug EXCRETION

• Potency: Refers to the amount of drug needed to

• Efficacy: Refers to the maximal response that can

Inferences of previous slide on relative analysis of drugs A, B, C,D.

 Drug A is more potent than drug B, but efficacy of both drugs

 Potency of drug C is more than drug D up to a certain dose.

 Efficacy of drug D is more than drug C because maximal

• DRC: Dose Response Curve

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