Toxicology: Nlom: Interactions

Front 1

In what way are humans normally exposed to chemicals?

Back 1

Humans are normally exposed to several chemicals at one time rather than to an individual chemical.

Front 2

? and ? exposure generally consists of multiple exposures.

Back 2

Medical treatment and environment exposure generally consists of multiple exposures.

Front 3

Hospital patients on the average receive how many drugs daily?

Back 3

Hospital patients on the average receive 6 drugs daily

Front 4

Home influenza treatment consists of what?

Back 4

Home influenza treatment consists of aspirin, antihistamines, and cough syrup taken simultaneously

Front 5

Drinking water may contain what?

Back 5

Drinking water may contain small amounts of pesticides, heavy metals, solvents, and other organic chemicals

Front 6

Air often contains what?

Back 6

Air often contains mixtures of hundreds of chemicals such as automobile exhaust and cigarette smoke

Front 7

Gasoline vapor at service stations is what?

Back 7

Gasoline vapor at service stations is a mixture of 40-50 chemicals

Front 8

Normally, how is the toxicity of a specific chemical determined?

Back 8

Normally, the toxicity of a specific chemical is determined by the study of animals exposed to only one chemical.

Front 9

Why is the toxicity testing of mixtures rarely conducted?

Back 9

Toxicity testing of mixtures is rarely conducted since it is usually impossible to predict the possible combinations of chemicals that will be present in multiple-chemical exposures.

Front 10

What is an interaction? Explain.

Back 10

The effect that one chemical has on the toxic effect of another chemical is known as an interaction.


Xenobiotics administered or received simultaneously may act independently of each other. However, in many cases, the presence of one chemical may drastically affect the response to another chemical. The toxicity of a combination of chemicals may be less or it may be more than would be predicted from the known effects of each individual chemical.

Front 11

There are four basic types of interactions. What are they based on? List them.

Back 11

Each is based on the expected effects caused by the individual chemicals.

1. Additivity

2. Antagonism

3. Potentiation

4. Synergism

Front 12

What is additivity?

Back 12

A combination of two or more chemicals is the sum of the expected individual responses.

Front 13

What is antagonism?

Back 13

Exposure to one chemical leads to the reduction in the effect of another.

Front 14

What is potentiation?

Back 14

Exposure to one chemical results in the other chemical producing an effect greater than if given alone.

Front 15

What is synergism?

Back 15

Exposure to one chemical causes a dramatic increase in the effects of another chemical.

Front 16

Chemical A produces a toxic effect of 20%.

Chemical B produces a toxic effect of 30%.

Chemical A and B together produces a toxic effect of 50%.

What kind of interaction is being observed when chemical A and B are taken together?

Back 16

Additivity.

Front 17

Chemical A produces a toxic effect of 20%.

Chemical B produces a toxic effect of 30%.

Chemical A and B together produces a toxic effect of 5%.

What kind of interaction is being observed when chemical A and B are taken together?

Back 17

Antagonism

Front 18

Chemical A produces a toxic effect of 0%.

Chemical B produces a toxic effect of 20%.

Chemical A and B together produces a toxic effect of 50%.

What kind of interaction is being observed when chemical A and B are taken together?

Back 18

Potentiation

Front 19

Chemical A produces a toxic effect of 5%.

Chemical B produces a toxic effect of 10%.

Chemical A and B together produces a toxic effect of 100%.

What kind of interaction is being observed when chemical A and B are taken together?

Back 19

Synergism

Front 20

List 4 ways that interactions can be described and categorized by their chemical or biological mechanisms?

Back 20

1. Chemical reactions between chemicals

2. Modifications in absorption, metabolism, or excretion

3. Reactions at binding sites and receptors

4. Physiological changes

Front 21

What is the most common type of drug interaction?

Back 21

Additivity is the most common type of drug interaction.

Front 22

List 3 examples of chemical or drug additivity reactions?

Back 22

1. Two central nervous system (CNS) depressants taken at the same time, a tranquilizer and alcohol, often cause depression equal to the sum of that caused by each drug.



2. Organophosphate insecticides interfere with nerve conduction. The toxicity of the combination of two organophosphate insecticides is equal to the sum of the toxicity of each.

3. Chlorinated insecticides and halogenated solvents both produce liver toxicity. The hepatotoxicity of an insecticide formulation containing both is equivalent to the sum of the hepatotoxicity of each.

Front 23

Antagonism is often a ? effect in toxicology and is the basis for most ?.

Back 23

Antagonism is often a desirable effect in toxicology and is the basis for most antidotes.

Front 24

Give an example of physiological antagonism.

Back 24

A severe drop in blood pressure resulting from a barbiturate can be reversed by administration of a vasopressor to increase blood pressure.

Front 25

Give an example of chemical antagonism.

Back 25

Mercure toxicity can be reduced by chelating (blinding) the mercure ions with dimercapol.

Front 26

Give an example of disposition antagonism.

Back 26

Swallowed poison is absorbed by introducing charcoal into the stomach.

Front 27

Give an example of receptor antagonism.

Back 27

Carbon monoxide poisoning is treated with oxygen which displaces the carbon monoxide from hemoglobin receptors.

Front 28

When does potentiation occur?

Back 28

Potentiation occurs when a chemical that does not have a specific toxic effect makes another chemical more toxic.

Front 29

Give 2 examples of potentiation.

Back 29

1. The hepatotoxicity of carbon tetrachloride is greatly enhanced by the presence of isopropanol. Such exposure may occur in the workplace.



2. Normally, warfarin (a widely used anticoagulant in cardiac disease) is bound to plasma albumin so that only 2% of the warfarin is active. Drugs which compete for binding sites on albumin increase the level of free warfarin to 4% causing fatal hemorrhage.

Front 30

Synergism can have serious what?

Back 30

Synergism can have serious health effects. With synergism, exposure to a chemical may drastically increase the effect of another chemical.

Front 31

Give 3 examples of synergism.

Back 31

1. Exposure to both cigarette smoke and radon results in a significantly greater risk for lung cancer than the sum of the risks of each.

2. The combination of exposure to asbestos and cigarette smoke results in a significantly greater risk for lung cancer than the sum of the risks of each.

3. The hepatotoxicity of a combination of ethanol and carbon tetrachloride is much greater than the sum of the hepatotoxicity of each.

Front 32

Different types of interactions can occur where for the same combination of two chemicals. Give an example.

Back 32

Different types of interactions can occur at different target sites for the same combination of two chemicals. For example, chlorinated insecticides and halogenated solvents (which are often used together in insecticide formulations) can produce liver toxicity with the interaction being additive.

The same combination of chemicals produces a different type of interaction on the central nervous system. Chlorinated insecticides stimulate the central nervous system whereas halogenated solvents cause depression of the nervous system. The effect of simultaneous exposure is an antagonistic interaction.

Front 33

Antagonism refers to an interaction in which:





There is an increase in a chemical's toxicity due to the presence of another chemical.




A reduction in a chemical's toxicity occurs due to the presence of another chemical.




Toxicity resulting from exposure to two or more chemicals equals the sum of the toxicities of the individual substances.

Back 33

Antagonism refers to an interaction in which a reduction in a chemical's toxicity occurs due to the presence of another chemical. An antidote interacts antagonistically with the toxic substance.

Front 34

A dose of 4 mg of an insecticide causes 20% toxicity whereas the same dose of another insecticide produces 30% toxicity. If 8 mg of a formulation containing both insecticides in equal concentrations causes 50% toxicity, the interaction is known as:





Additivity




Antagonism




Synergism

Back 34

A dose of 4 mg of an insecticide causes 20% toxicity whereas the same dose of another insecticide produces 30% toxicity. If 8 mg of a formulation containing both insecticides in equal concentrations causes 50% toxicity, the interaction is known as additivity. Additivity is the most common type of interaction, especially with substances that produce toxicity by the same method.

Front 35

Piperonyl butoxide added to pyrethrum insecticide results in a pyrethrum formulation having about 100 times the toxicity of pyrethrum alone. The interaction of this combination is:





Additivity




Antagonism




Synergism

Back 35

Piperonyl butoxide added to pyrethrum insecticide results in a pyrethrum formulation having about 100 times the toxicity of pyrethrum alone. The interaction of this combination is synergism. Synergists are used to enhance the toxicity of several commonly used insecticides.