Toxicology

Question 1

Toxicology

Answer 1

Toxicology is the qualitative and quantitative study of the adverse or toxic effect of chemicals and other anthropogenic materials or xenobiotics on organisms.

Question 2

Medical toxicology

Answer 2

Medical toxicology, is a medical subspecialty focusing on the diagnosis, management and prevention of poisoning and other adverse health effects due to medications, occupational and environmental toxicants, and biological agents.

Question 3

Toxicology

Answer 3

Toxicology is the study of poisons

Question 4

What are Poisons?

Answer 4

Poisons are chemical/physical agents that produce adverse responses in biological organisms
Any substance can be toxic if introduced in a dose capable of disturbing the normal physiological homeostatsis of the exposed body.

Question 5

What are Toxins?

Answer 5

Toxins: are poisonous substance produced within living cells or organism (a poison of natural origin) e.g. venom

Question 6

What is Poison (Toxicant)?

Answer 6

Poison (Toxicant) - a chemical that may harm or kill an organism

Question 7

What is Toxicity?

Answer 7

Toxicity – is the ability of a chemical agent to cause injury

Question 8

What Hazard?

Answer 8

Hazard – is the likelihood that injury will occur in a given situation or setting

Question 9

What is a Risk?

Answer 9

Risk – is defined as the expected frequency of the occurrence of an undesirable effect arising from exposure to a chemical or physical agent.

Question 10

What is a Synergism?

Answer 10

Synergism: combined effect is greater than the sum of individual effect

Question 11

What is Additive effect?

Answer 11

combined effect is equal to the sum of their individual effect

Question 12

What is Potentiation effect?

Answer 12

When one substance enhances the effect of another

Question 13

What is Antagonism?

Answer 13

When one substance decreases the effect of another

Question 14

What are Phase I: Biotransformation of poisons?

Answer 14

the drug is converted into more polar compound e .g oxidation, reduction, &hydrolysis

Question 15

What are Phase II (conjugation): Biotransformation of poisons?

Answer 15

a drug or its metabolite is conjugated with an endogenous substance e .g glucuronide conjugate

Question 16

What is Enzyme inhibition: Biotransformation of poisons?

Answer 16

by this the biotransformation of drugs is delayed & is a cause of increased toxicity

Question 17

What is Enzyme induction: Biotransformation of poisons?

Answer 17

by this the biotransformation of drugs is accelerated & is a cause of therapeutic failure

Question 18

Basic Classification of Toxicology

Answer 18

Descriptive toxicology: Descriptive toxicology deals with toxicity tests on chemicals exposed to human beings and environment as a whole.
Mechanistic toxicology : Mechanistic toxicology deals with the mechanism of toxic effects of chemicals on living organisms
Regulatory toxicology
Occupational toxicology
Environmental toxicology
Clinical toxicology: intentional consumption of poison
Forensic toxicology

Question 19

Basis for Grouping Toxicology

Answer 19

1. sources of poison
2. properties of poison
3. mechanism of toxicity
4. detection
5. clinical manifestations
6. Management

Question 20

Sources of Toxins

Answer 20

Chemical source: the commonest sources are drugs corrosives
Plant source : cocaine, cannabis
Animal source : the list but most serious source e.g. venomouse animals (snakes, scorpions, spiders, wasps)

Question 21

Venomous and Poisonous Animals

Answer 21

Venomous animals deliver or inject venom into other organisms, using a specialized apparatus such as fangs or a stinger
The venom is produced in a gland attached to this apparatus
Poisonous animals do not deliver their toxins directly.
The entire body or large parts of it may contain the poisonous substance.
The organism may be harmful when eaten or touched.

Question 22

What are Site of Toxic Actions?

Answer 22

Local (Non-specific): Wherever the poison contacts the biological system it starts its harmful effects. It does not require specific site or receptor to elicit its effects such as toxicity by acids or alkalis

Remote (systemic): The poison affects a system far from its portal of entry

Local and Remote: The poison has the capacity of acting locally and systemically.

Question 23

Duration and Frequency of Exposure

Answer 23

Acute: application of a single or short-term (less than a day) dosing of a substance to cause toxicity

Sub-acute: toxicity is expressed after repeated applications for a duration less than half-life expectancy of the substance

Chronic : Expression of toxic symptoms only after repeated exposure to a chemical in doses regularly applied to the organism for a time greater than half of its life expectancy

Question 24

Mechanisms of Toxicity

Answer 24

Direct : The poison itself can cause toxic effects as in corrosives
Indirect : toxicity results from the interactions of the poison with the biological activity within biological system
Binding to cell membrane to change in their function or structure thus affecting their normal activities
Interference with enzymatic actions
Formation of metabolites which are more toxic than the parent poison
Effect on DNA

Question 25

Classification of Toxic Agents

Answer 25

According to the target organ e.g. hepatotoxic, nephrotoxic According to their use e.g. food additives, pesticide, drug According to their source e.g. animal, plant According to their effects e.g. carcinogen, mutagen According to their physical state e.g. gas, liquid, solid According to their chemistry e.g. amine, hydrocarbon According to their poisoning potentiality e.g. extremely toxic, slight toxic According to their biochemical mechanism of action e.g. alkylating agent, acetyl cholinesterase inhibitor

Question 26

Factors Affecting Action of Poison

Answer 26

1. Factors related to the poison: Dose : a basic principle in toxicology Dose is the amount of chemical that comes into contact with the body or gets inside the body The increase in dose will increase the toxicity Physical status : gaseous state is more toxic than liquid state than the solid state Purity: this depends on the impurity of the poison If the impurities are more toxic than the poison, the toxicity will be more and vice versa. 2. Factors related to the individual : Age Health Sensitivity Sex 3. Factors related to mode of exposure Inhalation ---> IM ---> Ingestion ---> Skin Contact 4. Factors related to environment Temperature, pressure . humidity,

Question 27

Factors affecting Delivery

Answer 27

Absorption: * Distribution towards the target of action * Reabsorption * Toxicity Presystemic elimination : * Distribution away from the target * Excretion * Detoxication

Question 28

General Principles of Poison Management

Answer 28

The poison or class of poison involved. The clinical features associated with some common poisons may be specific Diagnoses other than poisoning must also be considered N.B General Physical examination should include – Vital signs – Evaluation of specific parts of the body Supportive measures:. - Maintain air way, adequate ventilation & oxygenation, provide tracheal intubation if required - If comatose, administer glucose, thiamine, &oxygen - For seizures, administer anticonvulsants Principles of toxin eliminations Inhalation , Skin, Oral sources , Force diuresis Dialysis

Question 29

Some Antidotes &Protective Agents used in the Treatment of acute Poisoning

Answer 29

Antidote: Atropine Poison: Organophosphate Antidote: Deferoxamine Poison: Iron Antidote: Methylene blue Poison: Nitrates Antidote: Physiostigmine Poison: Atropine Antidote: Naloxone Poison: Opioids Pyridoxine Poison: Isoniazid

Question 30

Analytical Toxicology

Answer 30

Detection, identification and quantification of poisons

Question 32

The roles of clinical toxicology laboratory

Answer 32

If the diagnosis is in doubt, The administration of antidotes or protective agents is contemplated, or The use of active elimination therapy is being considered. Drug monitoring

Question 32

Basic Information Required in toxicology laboratory

Answer 32

Suspected agent(s) Suspected dose Time of ingestion and sampling Clinical presentation: Location of the victim

Question 32

Samples Required for Toxicological Analysis from Autopsy

Answer 32

Blood The best place at autopsy is from femoral and iliac veins, then axillary veins in consequence No samples from Jugular vein: may be contaminated by reflux from upper thorax General body cavity: highly contaminated by intestinal contents Heart or great vessels in chest: postmortem diffusion of drugs and alcohol from the stomach or aspirated vomit can contaminate these sites Urine 20-30 mls of urine in sterile container without preservatives Faeces Used in heavy metals as arsenic, lead, mercury Vomit and Stomach contents

Question 32

Forensic Toxicology

Answer 32

Forensic toxicology is concerned with the detection and estimation of poisons for legal purposes Tissues and body fluids obtained at autopsy Blood, urine, or gastric material obtained from a living person Poison as a cause of death can be proven only with toxicological analyses that demonstrate the presence of the poison in the tissues or body fluids of the deceased Presence of poisons can be demonstrated only by the chemical methods of isolation and identification. If toxicological analyses are avoided, death may be ascribed to poisoning without definite proof

Question 33

Methods of Analysis (Qualitative)

Answer 33

Colour test Rapid easily performed, qualitative , screening test but not specific Can be used as bed side rapid test Examples Ferric Chloride test for salicylate: It gives pink colour Zwikker test for barbiturates: it gives purple color Formaldehyde-Sulfuric acid test for Benzodiazepines : It gives orange colour Mandalin test for opoid : It gives brown colour Immunoassays Chromatography