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DWT exam 3 > Toxicology intro > Flashcards

Toxicology intro Flashcards

1
Q

Toxicology

A

The study of the adverse effects of xenobiotic compounds (toxins and/or toxicants), including their chemical properties, biological effects and treatments

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2
Q

poison

A

Any substance capable of causing a deleterious response in a biological system

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3
Q

toxin

A

A poisonous substance that is a specific product of the metabolic activities of a living organism
* Antigenic poison or venom of plant or animal origin
* Subset of toxicants

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4
Q

dose

A

Amount of drug, toxin or toxicant that reaches the site or sites of action in an animal

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5
Q

ED50

A

Dose producing a therapeutic response in 50% of the population
effective dose

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6
Q

LD50

A

Dose causing death in 50% of the population

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7
Q

LC50

A

Concentration of a toxin/toxicant that will cause death in 50% of the population

We use these values to compare relative toxicities and estimate potency

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8
Q

bromethalin

A

rodentacide
uncouples ox phos, cells accumulate Na+, cells swell
neurotoxicity (cerebral and spinal cord edema) > paralysis

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9
Q

selenium deficiency

A

white muscle dz > cardiomypathy > death
skel muscle cannot sequester Ca2> calcification of tissue

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10
Q

selenium toxicity

A

Lethargy, tachycardia, sweating, teeth grinding

Hair loss, nail discoloration, hoof lesions lameness, emaciation, death

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11
Q

Zinc deficiency

A

Zinc-responsive dermatitis
* Alopecia
* Susceptible to skin infections

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12
Q

zinc toxicity

A

Intravascular hemolysis
GI irritation
Hemoglobinuria
Hematuria

penny ingestion

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13
Q

acute exposure

A

Exposure to a chemical for less than 24 hours
Usually a single dose occurring from a single incident
Death

ex:
* Iron overdoses in pigs
* Insecticide ingestion in animals

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14
Q

subacute exposure

A

Exposure to a chemical for one month or less
Repeated doses
ex:
* Dogs eating aflatoxin contaminated food for 4 weeks

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15
Q

Subchronic Exposure

A

Exposure to a chemical for 1 to 3 months
Repeated doses
ex: copper toxicity in sheep/dogs

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16
Q

Chronic Exposure

A

Exposure to a chemical for > 3 months to years
Repeated doses
ex: copper toxicity in sheep and dogs

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17
Q

aflatoxins

A

acute/subacute exposure
Ingestion of contaminated food (produced by fungus)
binds to hepatic proteins: hepatotoxicity
dogs, poultry most effected

18
Q

routes of exposure

A
  • oral
  • dermal
  • inhalation
  • paraenteral (IV, IP, IM, SQ)
19
Q

oral ingestion

A

Most common route of exposure in veterinary toxicology

Requires nearly all of the dose to pass through liver before reaching systemic circulation

20
Q

dermal route of exposure

A

topical, percutaneous
flea spray, using dog flea products on cats

21
Q

inhalation route of exposure

A

Lungs have large surface area, increased absorption

Avoids liver first pass effect
* Metabolism can occur in lungs (P450 enzymes)

birds very sensitive

22
Q

Why are birds sensitive to inhalation?

A

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 tissues

23
Q

absorption

A

Process by which toxins/toxicants cross membranes and enter the bloodstream
affected by:
* solubility
* ionization (unionized= lipid soluable)
weak acids= unionized (absorbed) in stomach
weak bases= unionized (absorbed) in intestines
* ruminant vs monogastric
* Gastric motility, secretion, and the rate of gastric emptying

24
Q

ruminants vs monogastrics absorption

A

Intake of nitrate and conversion to nitrite exceed microflora’s capacity to reduce nitrite
ruminants have different stomach compartments with different pH

25
Q

dermal route of absorption

A

Lipid-soluble compounds well-absorbed
Formulation in solvents can facilitate absorption

26
Q

distribution

A

When a drug or toxin/toxicant enters into systemic circulation by absorption, it gets distributedinto the body’s tissues

Depends on several things:
* Perfusion/blood flow through tissues
* Protein binding of drug
* Acidic drugs may bind protein and remain in circulation > low volume of distribution
* Basic drugs tend not to bind protein and are extensively taken up by tissues > larger volume of distribution

27
Q

distribution via bloodstream

A

Portal blood circulation > Liver
Poisons/drugs not equally distributed throughout body
* Tend to accumulate in specific tissues/fluids

Blood-brain barrier tends to exclude hydrophilic poisons/drugs

28
Q

distribution in blood brain barrier

A

Blood-brain barrier tends to exclude hydrophilic poisons/drugs

Younger animals more at risk due to immature BBB
ex: Lead poisoning in kittens – vertical nystagmus; muscle tremors/seizures

29
Q

ivermectin toxicity

A

collie breeds
Deficient in multi-drug resistance gene (MDR1) > P-glycoprotein
* P-glycoprotein functions as an efflux drug transport pump at the blood-brain barrier
* Ivermectin cannot be transported out of the brain in MDR1 deficient animals > acts as a GABA agonist

Drug accumulates in brain causing CNS depression
Ataxia, CNS depression, mydriasis

30
Q

lead toxicity

A

GI irritant, neurotoxicant (V/D, blindness, nystagmus)
Liver and kidney damage

Blood > Liver, Kidney, Brain > Bone

31
Q

metabolism

A

Conversion of lipophilic toxins/toxicants > hydrophilic chemicals
* Inactivate (detoxify) xenobiotic agent
* Activate xenobiotic agent to pharmacologically active metabolite

32
Q

metabolism phase 1 reaction

A

Functionalization reactions
Converts xenobiotic to a more polar metabolite through hydrolysis, reduction, or oxidation
In some cases, makes it more amenable to phase II biotransformation
May metabolize a xenobiotic agent to a toxic metabolite

33
Q

metabolism phase II reaction

A

Conjugation reactions
Conjugation of large, polar molecule to render xenobiotic hydrophilic for excretion
Does not always result in less toxicity or inactivation

34
Q

Methemoglobinemia

A

oxidative damage
tylenol
Cats have low methemoglobin reductase on RBCs
hepatotoxicity

35
Q

excretion

A

Kidneys > Urine
Bile > Feces
Milk

36
Q

milk excretion

A

Milk of cows tends to be slightly acidic + milk fat
pH 6.5 to 6.9 (relative to plasma – 7.2 to 7.4)
* Tends to concentrate basic, fat soluble toxicants/drugs
* Relay in toxicants to nursing calves, humans

37
Q

excretion ion trapping

A

Altering the urine pH to inhibit reabsorption of toxicants across the renal tubular membranes into the blood stream

To “trap” the toxicants in its ionized form in the urine so it will be excreted

Non-ionized toxicants can diffuse across cell membranes because of their lipid solubility; whereas ionized molecules cannot diffuse across lipid membranes

38
Q

chocolate toxicity in dogs

A

adenosine
* calming, vasodilation, prepare for sleep

caffeine, theobromine, theophylline (in chocolate)
* Inhibit adenosine and increase catecholamine release resulting in CNS stimulation, tachycardia, diuresis, smooth muscle contraction, vasoconstriction
* Cause release of dopamine and glutamate > excitatory neurotransmitters

Why are dogs predisposed?
* Long half-life of theobromine in dogs!
* Theobromine is metabolized into xanthine > methyluric acid by hepatic CYP450

39
Q

age affecting toxicity

A

Younger animals
* Blood brain barrier still immature – more permeable than adult
* GI motility immature
* Lower glomerular filtration rate
* Rumen microflora low

Older animals
* Decreased metabolic capacity
* Decreased kidney function

40
Q

pregnacy and lactation factor in toxicity

A

Hormone changes can affect metabolism
Circulatory changes can alter distribution
Increased susceptibility of fetus to some toxicants
Excretion of fat soluble chemicals in milk
* Organochlorines, fat soluble pesticides
* Lead
* Tremetone (White snakeroot toxins)

41
Q

disease conditions determining toxicity

A

Heart disease – cardiotoxic plants, feed additives
Kidney disease – decreased excretion
Liver disease
* Decreased metabolic detoxification
* Decreased proteins, e.g., albumin and clotting factors

DWT exam 3 (14 decks)

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