Introduction to Toxicology
Session 26: Introduction to Toxicology
Total Session Time: 120 minutes
Prerequisites
None
Learning Tasks
By the end of this session students are expected to be able to:
Define terms used in toxicology
Describe broad areas/branches of toxicology
Describe mechanisms of toxicology
Resources Needed:
Flip charts, marker pens, and masking tape
Black/white board and chalk/whiteboard markers
Computer and LCD projector
SESSION OVERVIEW
Activity/
Step
Time
Activity/
Content
Step
Time
Content
Step
Time
Method
Content
Method
Method
1
1
05 minutes
05 minutes
Presentation
Introduction, Learning Tasks
Introduction, Learning Tasks
Introduction, Learning Tasks
2
2
50 minutes
50 minutes
Presentation/
Definition of Terms Used in Toxicology
Definition of Terms Used in Toxicology
Definition of Terms Used in Toxicology
2
2
50 minutes
50 minutes
Buzzing
Definition of Terms Used in Toxicology
Definition of Terms Used in Toxicology
Definition of Terms Used in Toxicology
Buzzing
3
3
30 minutes
30 minutes
Presentation/
Description of
Broad Areas/Branches of
Broad Areas/Branches of
3
3
30 minutes
30 minutes
brainstorming
Toxicology
brainstorming
Toxicology
4
4
25 minutes
25 minutes
Presentation
Description of
Mechanisms of Toxicology
Mechanisms of Toxicology
5
5
05 minutes
05 minutes
Presentation
Key Points
6
6
05 minutes
05 minutes
Presentation
Evaluation
PST 05104 Pharmacology & Therapeutics 202 NTA Level 5 Semester 1 Facilitator Guide
SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning tasks and clarify
ASK students if they have any questions before continuing.
STEP 2: Definition of Terms Used in Toxicology (50 minutes)
Activity: Buzzing (5 minutes)
ASK students to pair up and buzz on the following question for 2 minutes
What is toxicology?
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
The followings are common terms/definitions used in toxicology
Toxicology:
o The science that investigates the adverse effects of chemicals on health.
o The field of toxicology is a broad-based multidisciplinary science that examines the harmful effects of substances on living organisms, including humans.
Poison:
o Is any substance that may disrupt biologic function and potentially kill an organism.
Toxin:
o Toxin, by strict definition, is a poison of biologic origin that does not have the ability to replicate.
o However, the term toxin has been used more loosely.
o For example, environmental toxin has been used to describe toxic substances of nonbiologic origin.
Venom:
o Is a toxin that is injected into the victim by some means (e.g., bee sting, snake bite).
Toxicant:
o Is a general term that refers to any harmful substance and is generally interchangeable with poison.
PST 05104 Pharmacology & Therapeutics 203 NTA Level 5 Semester 1 Facilitator Guide
Toxicodynamics:
Refers to the general concepts of pharmacodynamics (interaction with molecular targets and mechanisms of effects) as applied to interactions and mechanisms that generate toxic effects.
Toxicokinetics:
o Refers to the general concepts of pharmacokinetics (absorption, distribution, biotransformation, and elimination) as applied to toxic substances.
Toxicity:
o Is the ability of a chemical to damage an organ system, to disrupt a biochemical process, or to disturb an enzyme system.
Paracelsus theory:
―All things are toxic and there is nothing without poisonous qualities: it is only the dose which makes something a poison‖
STEP 3: Broad Areas/Branches of Toxicology (30 minutes)
Activity: Brainstorming (5 minutes)
Ask students to brainstorm on the following question:
What are branches of toxicology?
ALLOW few students to respond
WRITE their responses on the flip chart/ board
CLARIFY and SUMMARISE by using the content below
The field of toxicology is a broad-based multidisciplinary science that examines the harmful effects of substances on living organisms, including humans and has several major subdivisions as listed below:
Descriptive toxicology:
o Focuses on toxicity testing with the intent of defining the degree of risk associated with substances.
Environmental toxicology:
o Involves the detection and understanding of environmental pollutants and their effects on humans and other organisms.
Forensic toxicology:
Is primarily concerned with detection and quantification of toxic substances for legal purposes.
Mechanistic toxicology:
Is focused on determining the mechanisms by which substances exert toxic effects.
Regulatory toxicology:
PST 05104 Pharmacology & Therapeutics 204 NTA Level 5 Semester 1 Facilitator Guide
Uses toxicologic data to establish policies regarding exposure limits for toxic substances.
Medical or clinical toxicology:
Focuses on the diagnosis and treatment of toxic effects in humans.
STEP 4: Mechanisms of Toxicology (25 minutes)
Mechanisms of toxicity can be classified as follows:
Physical:
o The physical presence of the toxicant triggers reactions that are harmful (e.g., asbestos fibers in the lung).
Chemical:
o Toxicants react chemically with the tissues or body fluids such as blood to produce harmful effects (e.g., strong acids or bases cause burns).
Pharmacologic:
o Toxicants interact with endogenous pharmacologic pathways, resulting in inhibition or overstimulation (e.g., botulinum toxin inhibits release of acetylcholine to cause paralysis).
Biochemical:
o Toxicant reacts biochemically with cellular constituents to produce cellular damage (e.g., venom of many snakes contains phospholipases that destroy cell membranes).
Genomic (genotoxic):
o Toxicant alters the genetic material of the cell, resulting in disruption of function. Genotoxic substances may be mutagenic or carcinogenic.
Mutagenic (carcinogenic):
o Toxicants alter DNA structure or function sufficiently to cause mutations (benzene) or initiate and promote the development of cancers (polycyclic aromatic hydrocarbons such as benzo[a]pyrene, found in cigarette smoke).
Immunologic:
o Toxicant may trigger an immune response that leads to cellular damage (e.g., penicillin-induced hemolytic anemia) or conversely suppresses the immune system, causing an increased susceptibility to infection (e.g., procainamide-induced agranulocytosis).
Teratogenic:
o Toxicant alters foetal development, resulting in birth defects (e.g., phenytoin is associated with development of cleft lip).
PST 05104 Pharmacology & Therapeutics 205 NTA Level 5 Semester 1 Facilitator Guide
STEP 5: Key Points (5 minutes)
Drugs and chemicals produce toxicity by different mechanisms
There are different branches of toxicology resulted from different causes and mechanisms by which these toxicities occurs
STEP 6: Evaluation (5 minutes)
What is a toxicant?
What are branches of toxicology?
What are mechanisms by chemicals/drugs produce toxicity?
PST 05104 Pharmacology & Therapeutics 206 NTA Level 5 Semester 1 Facilitator Guide
References
Katzung, B. G. (2018). Basic and clinical pharmacology. New York: Mcgraw Hill Education.
Santos, R. R., Rang, H. P., Dale, M. M., Ritter, J. M., & Flower, R. J. (2007). Rang & Dale Farmacologia. Rio de Janeiro: Elsevier.
Tripathi, K. (2018). Essentials of Medical Pharmacology. Place of publication not identified:
Jaypee Brothers Medical P.
Ministry of Health and Social Welfare. (2013). Standard Treatment Guidelines & National Essential Medicines List Tanzania Mainland (4th ed.). Dar es salaam, Tanzania government printers.
Sally S.R, Jeanne C.S. (2000). Introductory Clinical Pharmacology (6th ed) New York, Lippincott Williams and Wilkins.
School of Pharmaceutical sciences. (2011).Tanzania Pharmaceutical Handbook (2nd ed.).
Dar es Salaam, ARDHI University press.
The Royal Pharmaceutical Society of Great Britain. (2007). Martindale, the Extra Pharmacopoeia (5TH ed). London, pharmaceutical press.
The Royal Pharmaceutical Society of Great Britain. 2009. British National Formulary (59th ed). London, BMJ Group and RPS Publishing.
PST 05104 Pharmacology & Therapeutics 207 NTA Level 5 Semester 1 Facilitator Guide
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