TOXICOLOGY
EXAM 1
STUDY GUIDE
toxicology
the study of poisons
-includes the identification of poisons, their chemical properties, and their biologic
effects as well as the treatment of disease conditions they cause
pharmacology and toxicology share many common principles including
-biodynamics of uptake and elimination
-mechanisms of action
-principles of treatment
can become poisons under certain conditions
therapeutic drugs and essential nutrients
the veterinary toxicologist deals with
-chemicals
-feed additives
-environmental contaminantss
-pesticides
-natural toxins of plant and animal origin
all which may adversely affect the health of animals
the clinical veterinary toxicologist is a specialist in
the cause, identification, and treatment of animal poisoning
,the toxicologist may have training in
-human medicine
-pharmacology
-physiology
-pathology
-chemistry
-the integration of these areas of knowledge is applied toward solving practical
problems
poison
any solid, liquid or gas that through either oral or topical routes, can interfere with life
processes of cells of the organism. This interference occurs by the inherent qualities of
the poison without mechanical action and irrespective of temperature
-molecular level, organism, or population
another term for poison
toxicant (less harsh; especially feed additives, drugs, etc.)
toxin
poisons that originate from biologic processes; generally classified as biotoxins but also
zoo toxins (animals, snakes, insects, etc.), mycotoxins (fungal), plants (phytotoxins),
algae (phycotoxins)
toxic
describes the effects of a poison on living systems
-"toxic effects of arsenic are related to the GI system and kidneys" (GIT and kidneys are
target organs)
toxicosis
describes the disease that results from exposure to a toxin. The term toxicosis is
often used interchangeably with the terms poisoning and intoxication
-"arsenic toxicosis is characterized by acute onset of vomiting and fluid to hemorrhagic
diarrhea"
toxicity
the amount of poison that, under specific conditions, causes toxic effects or detrimental
biologic changes
-ability to produce poisoning often expressed as mg toxicant per kg body weight..mg/kg
-the acute "toxicity" of arsenic is 5mg/kg body weight f
a major concept in toxicity is the relationship of
,dose and response: a toxic or adverse reaction to a chemical has a threshold
dose above which detrimental effects can be measured. Most toxic responses increase
in degree or severity (graded response) as dosage of intoxicant increases.
toxicity is usually expressed as
mg of toxicant per kg of body weight that will produce a defined biologic effect
dosage
the amount of toxicant per unit of animal weight
dose
the total amount of toxicant received per animal
toxicity and dosage in wildlife or fish
toxicity may be expressed as the concentration of the substance in the feed or water,
where dosage is directly correlated with concentration when the material is freely
available
lethal concentration (LC)
lowest concentration of compound in feed (or in water for fish) that causes death. it is
expressed as mg of compound per kg of feed and water
acute lethal toxicity
LC501 or concentration in feed or water that will kill 50% of animals exposed
highest nontoxic dose (HNTD)
largest dose not resulting in clinical or pathologic chemical-induced alterations
toxic dose-low (TDL)
lowest dose that will produce alterations; administration of twice this dose is not lethal
toxic dose-high (TDH)
dose that will produce drug-induced alterations and administration of twice this dose is
lethal
lethal dose
, lowest dose that causes death in any animal during the period of observation. Various
percentages can be attached to the LD value to indicate doses required to kill 1% (LD1),
50% (LD50)1, or 100% (LD100) of the test animals. LD50 is commonly used measure of
toxicity.
characteristics and limitations of the LD50
-quantal (all or none) response of a group
-straight line on semiology or prohibit paper
-lethal to 50% of animals by defined conditions
-does not address severity/clinical characteristics
-no
median lethal dose (MLD)
equivalent to the LD50 and can be used interchangeably with it
ED50 (effective dose 50)
dosage of a drug or therapeutic agent that produces the desired effect in 50% of a
population
expressions of safety for drugs are given by
comparisons of the LD50 to the ED50
therapeutic index (TI)
ratio of the LD50 to the ED50 (TI=LD50/ED50)
standard safety margin
more conservative and clinically relevant estimate than the TI; the SSM is the ratio of
the LD to the ED99 (SSM=LD1/ED99)
exposure and effects of toxicants are often defined by the
frequency and duration of exposure: acute, subacute, synchronic, chronic
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