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50 Cards in this Set

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  • Back
What is a poison?
Any substance causing injury by chemical or physicochemical means.
What is a bioassay?
An experiment to measure effects of chemicals in living systems.
What is toxicity?
The inherent capacity of a substance to produce injury.
What is risk?
The probability of an injury under defined exposure conditions.
What is safety?
The probablity of injury under defined exposure conditions (for example a sealed toxin is safer than one in an open beaker)
What is the basic premise of relative risk?
All actions invoke some risk. There is no life without risk.
What is the basic approach when considering relative risk?
Define acceptable level of risk. Determine a 'Virtually Safe Dose'.
What is a virtually safe dose?
In the US this is a dose of a chemical defined so that a lifetime exposure for excess death risk is no more than one in one million.
What is a hazard?
The nature of adverse or harmful effects; potential for causing harm. This incorporates toxicant's intrinsic activity.
What is risk?
[Hazard/Safeguards]. Likelihood (probability, odds) of injury based on actions or conditions of use or exposure.
What is relative risk?
Theoretical risk vs. Proven risk.
List the 4 aspects of Risk Assessment.
1. Hazard identification

2. Dose response assessments

3. Exposure assessment

...1-3 help characterize...

4. Risk characterization
What does Hazard Identification define?
Defines the nature and severity of effects.
What do dose response assessments look at?
Dose vs Incidence. You extrapolate from high to low doses (uncertainty involved). You extrapolate from animals to humans (uncertainty involved).
What do Exposure Assessments define?
They define exposure from all sources.
What does Exposure Assessment consider?
Considers uniquely susceptible populations.
What does Risk Characterization estimate?
Estimates the incidence in a defined population for a given exposure.
Define the difference between Risk Assessment and Risk Management?
Risk Assessment involves scientific experiments and judgements.

Risk Mgmt involves politics and people. Involves societal and political decisions.
What is the general philosophy of toxicology testing and risk assessment?
Humans are AT LEAST as sensitive as the most sensitive species tested. (this is because testing is primarily done on animals)
List 5 assumptions of laboratory animal testing?
1. Effects in lab animals apply to humans (or you have to explain the differences away scientifically)

2. Large database for animals (there is a lot of info on animals)

3. High dose exposure (there is relatively few lab animals tested vs the likely number of humans that will be exposed)

4. Dosage: per unit body wt (mg/kg) is convenient.

5. Dosage: per unit bsa (mg/m^2) better equates to human dosage.
What is a dilemma involved in extrapolating to very low doses?
Large doses of toxicants tested in a relatively small number of lab animals.

Verses...

Very large numbers of people exposed to relatively small doses of toxicants.

(this makes the jump from animal studies to humans a big challenge)
If a toxin has no threshold effect what will be observed on a graft?
The line representing the chemical will go through zero on the x and y axis. This means that as long as chemical is present there is a response.
Cancer causing agents are assumed to have no what?
No threshold.
When are safety evaluations generally applied?
In drug development.
What are the two purposes of drug development?
1. Identify ALL possible adverse effects.

2. To estimate an ACCEPTABLE exposure level.
What is NOEL?
Highest No Observed Effect Level (dose). This is derived from chronic animal studies. The effect being studied does not have to be an adverse effect.
What is NOAEL?
Highest No Observed ADVERSE Effect Level. This is derived from chronic animal studies. (what is considered an adverse effect needs to be defined)
What is an ADI?
Acceptable Daily Intake. This is calculated from NOEL, NOAEL, etc.
What is an Acute type of poisoning/testing defined as?
Single/very short term types of poisoning/testing. From minutes to hours, observe up to 14 days.
What is a Subchronic (subacute) type of poisoning/testing?
Short term/frequent exposure. From few days to few months, often 90 days.
This is often used as a pilot to a chronic study.
What is a chronic type of poisoning/testing?
Long term. Months to years ~ "lifetime exposures" are different for different animals. Agent or injury accumulates over time.
What is a local site of toxicant action?
Site of initial contact. Skins, Lungs, Eyes, Mucous membranes.
What is a systemic site of toxicant action?
Site other than the contact site. AKA 'general'. Implies absorption and distribution.
What is a target organ?
The organ(s) most likely responsible for outcome.
What needs to be identified in a safety evaluation?
The active/toxic form (metabolite)
What are idiosyncratic rxns?
A problem areas of safety evaluations. It is an unexpected sensitivity to low doses, or resistance to high doses not predicted by animal models.
Other than idiosyncratic rxns what else may be difficult to predict in safety evaluations?
Interactions and Delayed toxicity.
What is delayed toxicity?
When a drug that is being taken is discontinued and negative effects show up later on.
List 4 special studies?
1. Carcinogenicity and Mutagenicity. (Genotoxic vs. Nongenotoxic)

2. Reproduction and Teratology (multigeneration studies)

3. Behavioral toxicity

4. Immunotoxicity.
The concentration of toxicant at a site does not define what?
It does not, by itself, define a target organ. The target organ may be an organ other than the one where the highest concentration of drug is found.

For example, Lead is found in bones but this is not the target organ because this is not what causes death in lead poisoning.
The signs of poisoning do not always reflect what?
The signs of poisoning does not always directly reflect the site of action.

For example, Carbon Monoxide poisoning does not affect CNS (it acts on blood).
Human ? is unknown and not predictable with certainty.
Carcinogenicity
How do you calculate a Reference Dose?
RfD = NOAEL/ (UF * MF) = ADI

UF = uncertainty factor

MF = Modifying factor
What is the uncertainty/safety factor when human date is available?
10

[10 * population variance]

Means we assume a 10-fold spread in our pop.
What is the uncertainty/safety factor when adequate animal data is available?
100

[10 * animals to humans]
What is the uncertainty/safety factor used when there are 'other issues'? (other issues such as limited animal data, children exposed, feared effects, etc)
1000

[10 * high dose to low dose]
What is MF?
Modifying Factors. Where politics plays a role.
What do uncertainty factors provide?
They provide a large margin of safety.
What does risk management consider?
Drug safety, Air/water quality standards, pesticide tolerances/food additive levels.
What differentiates poison from remedy?
The right dose differentiates poison from remedy.