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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
dermal route of absorption
**Lipid-soluble** compounds well-absorbed Formulation in **solvents can facilitate absorption**
26
distribution
When a drug or toxin/toxicant enters into systemic circulation by absorption, it gets distributed into 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
distribution via bloodstream
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
distribution in blood brain barrier
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
ivermectin toxicity
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
lead toxicity
GI irritant, **neurotoxicant** (V/D, blindness, nystagmus) Liver and kidney damage **Blood > Liver, Kidney, Brain > Bone**
31
metabolism
Conversion of lipophilic toxins/toxicants > hydrophilic chemicals * Inactivate (detoxify) xenobiotic agent * Activate xenobiotic agent to pharmacologically active metabolite
32
metabolism phase 1 reaction
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
metabolism phase II reaction
Conjugation reactions **Conjugation of large, polar molecule to render xenobiotic hydrophilic for excretion** Does not always result in less toxicity or inactivation
34
Methemoglobinemia
oxidative damage tylenol Cats have low methemoglobin reductase on RBCs hepatotoxicity
35
excretion
Kidneys > Urine Bile > Feces Milk
36
milk excretion
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
excretion ion trapping
**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
chocolate toxicity in dogs
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
age affecting toxicity
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
pregnacy and lactation factor in toxicity
**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
disease conditions determining toxicity
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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