NTA Level 4 • Semester 2 • PST04211

Introduction to Pharmacology

Basic Pharmacology • Source Session/Topic 1

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Session 1: Introduction to Pharmacology

Total Session Time: 120 minutes

Prerequisites

• None

Learning Tasks

By the end of this session students are expected to be able to:

• Define the terms pharmacology, drug and pro-drug and medicine

• List sources of drugs

• Define the term pharmacokinetics and list pharmacokinetics Parameters

• Explain bioavailability and half life of drugs

• Define pharmacodynamic, receptor, agonist, antagonist and synergy

• Explain terms toxic, therapeutic dose and therapeutic index

• Define the terms tolerance, habituation, dependence and addiction

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board and chalk/whiteboard markers

• Overhead projector and Computer

SESSION OVERVIEW

Activity/

Step Time Content

Method

1 05 minutes Presentation Introduction, Learning Objectives

Definition of Pharmacology, Drug and

2 10 minutes Presentation/Buzzing

Pro-drug and medicine

3 10 minutes Presentation/Brainstorming Sources of Drugs

Definition of Pharmacokinetics and

4 20 minutes Presentation

Pharmacokinetics Parameters

5 15 minutes Presentation Bioavailability and Half-life of Drugs

Pharmacodynamics, Receptor, Agonist,

6 15 minutes Presentation

Antagonist and Synergy

Toxic Dose, Therapeutic Dose and

7 15 minutes Presentation

Therapeutic Index

Tolerance, Habituation, Dependence and

8 20 minutes Presentation

Addiction

9 05 minutes Presentation Key Points

10 05 minutes Presentation Evaluation

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide 1

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Objectives (5 minutes)

READ or ASK students to read the learning objectives and clarify

ASK students if they have any questions before continuing.

STEP 2: Definition of Pharmacology, Drug and Pro-drug (10 minutes)

Activity: Buzzing (5 minutes)

ASK students to pair up and buzz on the following questions for 5 minutes

• What is Pharmacology?

• What is a drug?

• What is a Pro-drug?

• What is a medicine?

ALLOW few pairs to respond and let other pairs add on points not mentioned

WRITE their response on the flip chart/board

CLARIFY and SUMMARIZE by using the content below and define other terminologies

not defined by students

• Pharmacology is a study of the effects of chemical substances on the function of living

systems

• A drug may is a substance that brings about a change in biologic functions through its

chemical actions

• A pro-drug is a chemical that is converted to active drug/form by biologic processes

inside the body

• A medicine is a chemical preparation, which usually but not necessarily contains one or

more drugs, administered with the intention of producing a therapeutic effect

• Medicines usually contain other substances (i.e. excipients, stabilisers, solvents, etc.)

besides the active drug, to make them more convenient to use

• In everyday parlance, the word drug is often associated with addictive, narcotic or mind-

altering substances-an unfortunate negative connotation that tends to bias opinion against

any form of chemical therapy

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

STEP 3: Sources of Drugs (10 minutes)

Activity: Brainstorming (5 minutes)

Ask students to brainstorm on the following question:

• What are sources of drugs?

ALLOW few students to respond

WRITE their responses on the flip chart/ board

CLARIFY and SUMMARISE by using the content below

• Drugs obtain from various sources such as: synthetic chemicals, chemicals obtained from

plants, fungal sources, animal sources, marine organisms or products of genetic

engineering

• Plant-derived drugs include: quinine, digitalis, atropine, ephedrine, strychnine, vinca

alkaloids and others which result from purification of active compounds from these

plants. For example, morphine which is purified from opium

• Fungal-derived sources include penicillin, streptomycin and many other antibiotics.

• Animal-derived sources include Insulin, fats containing nutrients/vitamins derived from

fish and others

• Natural products, derived mainly from fungal and plant sources, have proved to be a

fruitful source of new therapeutic agents, particularly in the field of anti-infective,

anticancer and immunosuppressant drugs

• Semi-synthetic drugs are derived from chemical modification of natural products for

example Beta-Lactam antibiotics such as cephalosporins

• Nowadays drugs are derived from chemical modifications/reactions in laboratories

STEP 4: Definition of Pharmacokinetics and Pharmacokinetics

parameters (20 minutes)

• Pharmacodynamics is define as actions of the drug on the body

• Pharmacokinetics is define as the actions of the body on the drug

• When a drug is administered it must be absorbed into blood from its site of

administration, distributed to its site of action, metabolized (mainly by the liver and other

processes) and finally eliminated from the body by excretion and other processes

• In short pharmacokinetics (PK) = Absorption (A), Distribution (D), Metabolism (M) and

Elimination (E). Therefore, PK=ADME

• The common terms used in description of pharmacokinetics are: Bioavailability (F) for

absorption, Volume of distribution (Vd) for distribution, extraction ratio (ER) for

metabolism and Clearance (CL) for elimination

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

STEP 5: Bioavailability and Half-life of Drugs (15 minutes)

• Bioavailability is the fraction of administered drug that reaches systemic circulation. For

example, if 100mg of a drug is administered orally and 80mg of the drug is absorbed, the

bioavailability is 80% or 0.8

• The capital letter F is used to represent bioavailability

• When a drug is administered through intravenously, all of the amount reaches systemic

circulation, and thus bioavailability is 100% or 1

• Half-life (t1/2) is the time required for the concentration of drugs in the body (blood) to

remain to half of the original concentration

• Half-life is useful in designing drug dosage regimens, predicting elimination (clearance)

and distribution of a drug (volume of distribution)

STEP 6: Pharmacodynamics, Receptor, Agonist, Antagonist and Synergy

(15 minutes)

• Pharmacodynamics refers to the relationship between drug concentration at the site of

action and the resulting effect, including the time course and intensity of therapeutic and

adverse effects

• A drug receptor is a specialized target macromolecule, present on the cell surface

intracellularly, that binds a drug and mediates its pharmacological actions

• Receptors are the sensing elements in the system of chemical communications that

coordinates the function of all the different cells in the body

• Most drugs must bind to their specific receptors which is followed by a sequence of

events before producing their effects

• The effect of a drug present at the site of action is determined by that drug‘s binding with

a receptor

• An agonist is a drug which binds to and activate the receptor to bring a pharmacological

effect directly or indirectly

• Antagonist are drugs which act by binding to receptors and therefore prevent the binding

of other molecules or drugs to the receptor resulting into diminished/reduced/blocked

effects of the molecules or drugs

• The effect of one drug is diminished or completely abolished in the presence of another

• Many therapeutically useful drugs act, either as agonists or antagonists, on receptors for

known endogenous mediators

• Drug synergy occurs when drugs can interact in ways that enhance or magnify one or

more effects, or side-effects, of those drugs

• Drug interactions can lead to synergetic (when the drug's effect is increased) or

antagonistic (when the drug's effect is decreased) effects

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

STEP 7: Toxic Dose, Therapeutic Dose and Therapeutic Index (15 minutes)

• Therapeutic dose is the dose that produces a clinically desired or effective response.

• Toxic dose is the dose that produces toxicity

• Therapeutic index (TI) of a drug is the ratio of the dose that produces toxicity to the dose

that produces a clinically desired or effective response

• Therapeutic Index=Toxic dose/Effective dose=TD/ED

• Therapeutic index is a measure of drug‘s safety. The higher the TI indicates that there is a

wider margin between doses that are effective and doses that are toxic

• The higher TI the higher the safety of the drug and vice versa

STEP 8: Tolerance, Habituation, Dependence and Addiction (20 minutes)

• The term tolerance is used to describe a more gradual decrease in responsiveness to a

drug, taking days or weeks to develop

• Generally, tolerance is the decrease in pharmacological effect on repeated administration

of the drug

• Drug dependence describes the state when drug-taking becomes compulsive, taking

precedence over other needs, often with serious adverse consequences. This involves

physical and psychological dependence

• Drug dependence is viewed as a reversible pharmacological phenomenon whereas

addiction is a chronic, relapsing human condition, a distinct from acute illness that can be

cured by abstinence

• Habituation or adaptation is a process which occur when a drug is given repeatedly or

continuous, such that cessation of the drug has an aversive effect, negative reinforcement,

from which the subject will attempt to escape by self-administration of the drug

STEP 9: Key points (5 minutes)

• Pharmacology is the study of the effects of chemical substances on the function of living

systems

• A drug is defined as a chemical substance of known structure, other than a nutrient or an

essential dietary ingredient, which, when administered to a living organism, produces a

biological effect

• Drugs and medicines can be obtained from natural and synthetic sources

• Pharmacokinetics (PK) involves Absorption (A), Distribution (D), Metabolism (M) and

Elimination (E).Therefore PK=ADME

• Therapeutic index is a measure of drug‘s safety

• Prolonged drug use may be associated with tolerance, dependence and addiction

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

STEP 10: Evaluation (5 minutes)

• What is Pharmacology?

• What is a drug?

• What is a pro-drug?

• What are the main sources of drugs?

• What is Pharmacokinetics?

• What is drug bioavailability?

• What is half-life of drugs?

• What is pharmacodynamics?

• What is therapeutic index?

• What do you understand by the terms tolerance, habituation, dependence and addiction?

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

References

Katzung, Bertram G, Masters, Susan B, & Trevor, Anthony J. (2006). Basic & clinical

pharmacology (10th Ed).

Ministry Of Health and Social Welfare. (2013). Standard Treatment Guidelines &

National Essential Medicines List Tanzania Mainland (4th ed.). Dar es salaam, Tanzania

government printers

Rang, H. P., Ritter, J. M., Flower, R. J., & Henderson, G. (2014). Rang & Dale's

Pharmacology: Elsevier Health Sciences.

Sally, S.R, Jeanne C.S. 2000. Introductory Clinical Pharmacology (6th ed) New York,

Lippincott, W., Wilkins R. & M (year) Title, Journal/Book; Publisher.

PST 04211 Basic Pharmacology NTA Level 4 Semester 2 Facilitator Guide

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