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Toxicology Flashcards

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1
Q

Toxicology

A

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

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2
Q

Medical toxicology

A

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.

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3
Q

Toxicology

A

Toxicology is the study of poisons

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4
Q

What are Poisons?

A

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.

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5
Q

What are Toxins?

A

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

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6
Q

What is Poison (Toxicant)?

A

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

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7
Q

What is Toxicity?

A

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

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8
Q

What Hazard?

A

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

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9
Q

What is a Risk?

A

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

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10
Q

What is a Synergism?

A

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

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11
Q

What is Additive effect?

A

combined effect is equal to the sum of their individual effect

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12
Q

What is Potentiation effect?

A

When one substance enhances the effect of another

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13
Q

What is Antagonism?

A

When one substance decreases the effect of another

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14
Q

What are Phase I: Biotransformation of poisons?

A

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

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15
Q

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

A

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

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16
Q

What is Enzyme inhibition: Biotransformation of poisons?

A

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

17
Q

What is Enzyme induction: Biotransformation of poisons?

A

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

18
Q

Basic Classification of Toxicology

A

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

19
Q

Basis for Grouping Toxicology

A
  1. sources of poison
  2. properties of poison
  3. mechanism of toxicity
  4. detection
  5. clinical manifestations
  6. Management
20
Q

Sources of Toxins

A

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)

21
Q

Venomous and Poisonous Animals

A

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.

22
Q

What are Site of Toxic Actions?

A

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.

23
Q

Duration and Frequency of Exposure

A

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

24
Q

Mechanisms of Toxicity

A

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

25
Q

Classification of Toxic Agents

A

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

26
Q

Factors Affecting Action of Poison

A
  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,
27
Q

Factors affecting Delivery

A

Absorption:
* Distribution towards the target of action
* Reabsorption
* Toxicity

Presystemic elimination :
* Distribution away from the target
* Excretion
* Detoxication

28
Q

General Principles of Poison Management

A

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

29
Q

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

A

Antidote: Atropine
Poison: Organophosphate

Antidote: Deferoxamine
Poison: Iron

Antidote: Methylene blue
Poison: Nitrates

Antidote: Physiostigmine
Poison: Atropine

Antidote: Naloxone
Poison: Opioids

Pyridoxine
Poison: Isoniazid

30
Q

Analytical Toxicology

A

Detection, identification and quantification of poisons

31
Q
A
32
Q

The roles of clinical toxicology laboratory

A

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

32
Q

Basic Information Required in toxicology laboratory

A

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

32
Q

Samples Required for Toxicological Analysis from Autopsy

A

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

32
Q

Forensic Toxicology

A

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

33
Q

Methods of Analysis (Qualitative)

A

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

Chem Path (25 decks)

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