Intro to Toxicants and Basic Concepts

Question 1

describe the study of toxicants (poisons)

Answer 1

the study of the ADVERSE effects of agents on living organisms via identification, chemical properties, biological effects, and intervention/prevention

Question 2

what is a toxicant? contrast with toxin

Answer 2

a toxicant is a catch all term for all poisons; a toxin is specifically a naturally produced toxicant (all toxins are toxicants, but not all toxicants are toxins)

Question 3

what are the 2 categories of toxicants? give 5 examples of the first and 4 examples of the second category

Answer 3

1. non-naturally produced toxicants: pesticides, pharmaceuticals, food additives, solvents, and environmental contaminants
2. naturally produced toxicants (bio toxins): plants (phytotoxins), fungal (mycotoxins), bacterial (exotoxins), and animals/insects (venoms)

Question 4

give the top ten of the “hit list” calls to APSCA animal poison control center in 2023

Answer 4

1. OTC human medications
2. human food and drink (drink new bc health drink craze)
3. human prescription meds
4. chocolate
5. vet products and meds (major increase bc boutique med offers all sorts of new products)
6. plants and fungi
7. household products
8. rodenticides
9. insecticides
10. recreational drugs (huge increase in last 5 years due to legalization)

Question 5

describe >90% of toxicant exposures of dogs and cats; and then 70-95%

Answer 5

> 90%: accidental, acute, at home and/or near home

75-90%: acute ingestion of single substance is most common, with acute dermal exposure in second place

Question 6

when is the highest incidence of toxicant exposure in dogs and cats? when is there a spike during the year?

Answer 6

highest incidence: may-august (summer)

spike: in december

Question 7

is there a gender/breed disposition to toxicant exposure in dogs and cats? what about age?

Answer 7

no gender or breed; but young/adult dogs (<4 years) are more common

Question 8

describe the illness and severity of toxicant exposures in 4 categories for dogs and cats

Answer 8

57-63% result in no signs

25-27% develop mild signs

7-8% develop moderate signs

1-3% develop major signs, death

Question 9

what are the top 3 toxicant agents causing death in dogs and cats?

Answer 9

1. organophosphate insecticides
2. ethylene glycol
3. anticoagulant rodenticides

Question 10

what is a target of a toxicant?

Answer 10

where a toxicant produces its effect (location)

can have a target site: molecular, or subcellular organelle

or a target cell/tissue: cell types targeted

or a target organ: can be localized to one organ or multiple organs

Question 11

give an example of a target species of toxicants; contrast to a target species

Answer 11

pesticides; that is their intended use is to kill pests; whereas a non-target species is the unintentional victims (cat ate rat with rat poisoning, etc.)

Question 12

define toxicosis, toxicity, toxic, and intoxication

Answer 12

toxicosis: illness or disease state

tocixity: the amount or quantity that produces the adverse effect (measurable amount/dose); related to body weight, time, present in feed, water, or air, and assays

toxic: how bad it is

intoxication: state of being intoxicated (poisoned)

Question 13

what are the 3 characteristics of toxicosis?

Answer 13

1. timing: immediate vs delayed
2. severity: reversible vs irreversible
3. spread: local vs multi-systemic

Question 14

describe the 4 durations of exposure

Answer 14

1. acute: exposure last less than 24 hours (can be single or multiple exposures within this time frame)
2. sub-acute: multiple or continuous exposures over less than 1 month
3. sub-chronic: multiple or continuous exposures greater than 1 but less than 3 months
4. chronic: multiple or continuous exposures over longer than a 3 month period

Question 15

what is relay toxicosis?

Answer 15

animal to animal, often in a predator prey relationship

Question 16

describe the concept of bioaccumulation and biomagnification

Answer 16

increased retention of toxic residues moving up the food chain where bioaccumulation and bioconcentration results in biomagnification of the toxic residue

Question 17

list and describe the 3 assays of toxicity

Answer 17

1. LD50: dose to be lethal for 50% of a population
2. TD50: dose to be toxic for 50% of a population
3. LC50: amount of an inhaled chemical to be lethal for 50% of a population

Question 18

describe the 5 categories of LD50

Answer 18

if LD50 is
>1000mg/kg: practically nontoxic (unless easy to abuse or highly available)
<1000mg/kg: mid/slightly toxic
<500mg/kg: moderately toxic
<50mg/kg: highly toxic
<1mg/kg: severely/extremely toxic

Question 19

compare and contrast individual dose-response relationship with population dose-response relationship

Answer 19

individual: a graded scale with a spectrum of responses where the severity increases with increasing doses; does not show individual variation; allows us to find the non-toxic versus toxic dose in ONE individual

population: can either have a single-dose or a single-endpoint

single-dose population: allows us to look at different responses and identify hyper and hyposensitive individuals in a population

single-endpoint: looks at one outcome and examines an increasing range of doses to determine minimal dose, maximal dose, LD50, therapeutic index, and margin of safety

Question 20

describe therapeutic index and margin of safety; which is safer to use?

Answer 20

therapeutic index is the ration of lethal dose over effective dose for most pop the population(could be LD50/ED50)

margin of safety is often calculated as LD1/ED99, or the dose it takes to kill 1% of the population over the effective dose of 99% of the population; is much safer

Question 21

describe threshold theory

Answer 21

the point at which the detoxification pathways and/or repair mechanisms are saturated or overwhelmed and an adverse effect is first observed

threshold dose is the theoretical dose where the D-R curve approaches the x-axis, or 0% adverse effect

example is chemotherapy

Question 22

why is the dose-response relationship important? (2)

Answer 22

1. tells whether there will be toxicity at a certain dose/level of exposure
2. tells if, when, and how to treat based on the level of toxicity of the dose