Principles of Toxicology Flashcards
Father of Toxicology
Paracelsus- Swiss physician
toxic
something poisonous, or causes adverse effects
toxicology
the study of poisons
concerned with identification, treatment and assessing risks of poisons
toxicant
compounds that cause toxicity
may be natural or man-made xenobiotic
xenobiotic
foreign substance
antidote
- remedy to counteract poison
- usually refers to any substance that prevents/relieves the effects of a toxicant
- no antidote works on all toxins and some can be potentially harmful
toxins
consist of manmade chemicals and natural products
classify as extremely toxic
< 1 mg/kg
ex: botulism, strychnine
classify as highly toxic
1-50 mg/kg
ex: nicotine
classify as moderately toxic
50-500 mg/kg
ex: aspirin, foxglove, acetaminophin
classify as slightly toxic
0.5-5 g/kg
ex: salt, grapes
classify as practically non-toxic
5-15 g/kg
classify as relatively harmless
> 15 g/kg
ex: water
additive chemical interaction
sum of the effects
1 + 1 = 2
antagonistic chemical interactions
blocks or brings down the negativity of the effects
1 + 1 = 1
synergistic chemical interaction
compounds work together and significantly increase the effects
1 + 1 = 4
factors related to the toxicant
- chemical structure
- affinity for some molecules
- what the toxicant is mixed in (carrier, adjuvant)
factors related to exposure
- dose
- route of entry
- duration of exposure
factors related to the subject
- species
- age of animal (young and old more susceptible)
- health status
- prior exposure
- physiological complications
factors related to the environment
-
climate/temperature
- chemicals degrade faster at higher temperatures, body temp dictates how drugs are metabolized
-
pH of stomach
- affects absorption of chemicals
examples of species differences
- cats deficient in glucuronidation
- dogs deficient in acetylation
- pigs deficient in sulfation
- pregnancy also alters metabolism
acute exposure
single dose exposure or several doses within a 24 hour period
sub-acute/subchronic exposure
exposure over 7-90 days
chronic exposure
protracted exposure (6 months - lifetime)
dose-response relationship
- central concept of toxicology
- assumes a cause and effect relationship and that response is proportional to dose
4 concepts important to toxicokinetics
- Absorption
- Distribution
- Excretion
- Metabolism
most important veterinary toxicants are absorbed via which routes?
oral and dermal
job of metabolism
detoxifies a compound and increases its elimination
bioactivation
- when metabolism increases the toxicity of a compound
- ex: benzoapyrene, aflatoxin, acetaminophen
- also happens with some drugs
4 steps in the mechanism of toxicity
- delivery from site of exposure to target
- reaction of the ultimate toxicant with the target molecule
- cellular dysfunction and resultant toxicities
- repair (apoptosis, tissue regeneration) or disrepair (tissue necrosis, fibrosis, cancer)
2 main ways toxicants cause toxicity
- cellular damage (can result from free radical damage, inhibition of energy production, disruption of enzyme function)
- organ system dysfunction (not associated with specific cellular injury, but lethal to intact organism)
10 of the most dangerous foods for dogs
- alcohol
- avocados
- chocolate
- coffee and caffeine
- fruit with pits and seeds
- grapes and raisins
- macadamia nuts
- garlic and onions
- xylitol
- yeast dough
