Toxocology Flashcards
Toxicology
Study of adverse effects of xenobiotic compounds
• including:
- chemical properties
- biological effects,
- Tx
Poison
Any substance capable of causing a DELETERIOUS RESPONSE in a
biological system
Toxin
Poisons that originate FROM LIVING ORGANISMS
(i.e., zootoxins from
animals, phytotoxins from plants, bacterial toxins)
Toxicant
Toxic substances, chemicals produced by HUMAN-MADE activities
Factors Determining Toxicity
- Dose
- Duration/Frequency of Exposure
- Route of Exposure
- Toxicokinetics (ADME)
- Physiological Factors
Dose
AMOUNT of drug, toxin or toxicant that REACHES THE SITE OF ACTION in an animal
LD50 vs LC50
??
Hormesis
Essential nutrients or non-nutritional toxic substances imparting beneficial effects, but ADVERSE EFFECTS AT HIGH OR LOW DOSES
- Selenium
- Zn
Acute Exposure
– Exposure to a chemical for < 24 hrs
– SINGLE DOSE occurring from a single incident
• Iron overdoses in pigs
• Insecticide ingestion in animals
Subacute Exposure
– Exposure to a chemical for < 1 month
– Repeated doses
• Dogs eating aflatoxin contaminated food for 4 weeks
Subchronic Exposure
Exposure to a chemical for 1 - 3 months
Chronic Exposure
Exposure to a chemical for > 3 months to years
Why are birds more sensitive to gases?
– Highly efficient at exchanging gases for high oxygen delivery to muscles for flight
– High metabolic rates, small size
– The air breathed is rapidly distributed to tissue
Parenteral Routes
1 - IV 2- inhalation 3- IP 4- SQ 5- IM
Which parenteral routes pass thru the liver before going to the body?
Intraperiotoneal
• used to experimentally mimic oral exposure
What does ADME stand for?
A - absorption
D - distribution
M - metabolism
E - excretion
What factors is most important regarding absorption of a toxin/toxicant?
Solubility
- Depends on the degree of ionization @ specific pH value = pKa of drug
Non-ionized drugs are ____ soluble?
Lipid soluble
Lipophilic toxicants
OP/carbamate insecticides
• Lipophilic
Insoluble salts
Barium sulfate = contrast radiography
pH of:
- Rumen
- Reticulum
- Omasum
- Abomasum
- Rumen
• 5.4 - 6.8
- Reticulum
• 2
- Omasum
• 5.4 - 6.8
- Abomasum
• 2 - 4Hay containing > 1% nitrate in rumen —> …?
Normally the Ruminal flora converts Nitrate –> nitrite –> ammonia to protein
• ↑ Nitrate conversion excess microflora capacity
- -> Nitites absorbed in blood
- -> oxidized Hb
- -> Methemoglobin cannot release O2 to tissues
- -> cyanosis + metHb-emia!!
How does GI motility affect drugs ADME?
↓ gastric motility / emptying
–> ↑ absorption
How can you prevent absorption?
- Emesis
- - xylazine / apomorphine - Activated charcoal + cathartic (accelerate defecation)
