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Toxicology Flashcards

Identify, diagnose, and manage toxic exposures by understanding mechanisms of toxicity, common poisons, antidotes, and species-specific susceptibilities. (49 cards)

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1
Q

4-methylpyrazole is the antidote for which toxin?

A

Ethylene glycol

(4-methylpyrazole (4-MP) is also called fomepizole)

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2
Q

Which two life-threatening serum biochemical abnormalities can occur if cats or small dogs receive phosphate-based enemas?

A
  • Hyperphosphatemia
  • Hypocalcemia

Hypocalcemia causes the more severe (potentially life-threatening) clinical signs.

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3
Q

What is the diagnostic blood test of choice, and the expected abnormality, in a case of organophosphate intoxication?

A

Serum acetylcholinesterase levels; low levels (< 50% normal) are consistent with intoxication

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4
Q

What is the typical acid/base abnormality found with ethylene glycol toxicosis?

A

Metabolic acidosis

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5
Q

Which gene mutation is responsible for susceptibility to ivermectin toxicosis in Collies?

A

MDR-1 gene (officially known as ABCB1)

(codes for P-glycoprotein)

P-glycoprotein on vascular endothelial cells normally actively pumps certain drugs, including ivermectin, out of the CNS, limiting their penetration. Without it, ivermectin reaches neurotoxic levels in the brain/CSF, even at standard doses.

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6
Q

What is the site of action, and the effect, of Clostridium botulinum toxin?

A

Site: Neuromuscular junction
Effect: Prevents presynaptic release of acetylcholine

The result is a flaccid paralysis, as well as autonomic nervous system disturbances.

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7
Q

What is the antidote for organophosphate intoxication?

A

Atropine and/or pralidoxime (2-PAM)

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8
Q

Which organ systems are affected in aminoglycoside toxicity?

A
  • Renal
  • Auditory
  • Vestibular
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9
Q

Brightly-colored ornamental beads made from tropical seed pods and used for jewelry classically contain which toxin?

A

Ricin

(castor bean)

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10
Q

Does chocolate toxicosis cause an increase or a decrease in central nervous system activity?

A

Increase

(until terminal)

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11
Q

Foxglove, lily of the valley (Convallaria majalis), and oleander (Nerium oleander) plants all contain the same toxic agent.

What is it?

A

Digitalis glycosides

Causing cardiac arrhythmias, anorexia, lethargy, and nausea.

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12
Q

Bromethalin rodenticide intoxication affects which body system?

A

Central nervous system

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13
Q

When beginning warfarin treatment for anticoagulation, why can a slightly procoagulant state occur initially (first 24-48 hours)?

A

Warfarin initially antagonizes proteins C and S, which are natural anticoagulants

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14
Q

What are the toxic components of chocolate?

A

Two methylxanthine alkaloids:

  • Theobromine
  • Caffeine
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15
Q

Name the photodynamic compound that is involved in cases of hepatogenic photosensitization.

A

Phylloerythrin

It accumulates in the skin and, when exposed to UV light, causes local phototoxic damage.

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16
Q

What are the two most common sites of nonsteroidal antiinflammatory toxicosis in horses?

A
  • Gastrointestinal (specifically, gastric ulcers and right dorsal colitis)
  • Renal (specifically, papillary crest necrosis)
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17
Q

What is the most common adverse effect of acetaminophen? Are dogs or cats more susceptible to an equivalent dose?

A
  • Methemoglobinemia, causing life-threatening hemolytic anemia
  • Cats are much more susceptible to toxic effects

Acetaminophen is also hepatotoxic. Cats develop toxicosis at lower doses and have more severe signs at equivalent dose.

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18
Q

Which production animal species is most susceptible to copper poisoning? Is acute or chronic more common?

A

Sheep; chronic

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19
Q

What is an outcome of raisin ingestion in dogs, lily ingestion in cats, or gentamicin administration in horses?

A

Acute renal failure

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20
Q

Horses that ingest plants containing pyrrolizidine alkaloids may develop toxicosis involving which organ system?

21
Q

What is the mechanism of toxicity of strychnine?

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A
  • Competitively and reversibly inhibits glycine (inhibitory neurotransmitter) at postsynaptic neuronal sites in spinal cord and medulla
  • Results in extensor muscle rigidity and tonic-clonic seizures
22
Q

Other than gastrointestinal and adrenal effects, ketoconazole is recognized to have toxic potential involving which important organ?

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A

Liver

And less commonly, it can also affect bone marrow, causing thrombocytopenia.

23
Q

Anticoagulant rodenticides inhibit the activation of which coagulation factors?

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A
  • Factor II
  • Factor VII
  • Factor IX
  • Factor X

The vitamin K-dependent factors, because the MOA of anticoagulant rodenticides is to inhibit the enzyme vitamin K epoxide reductase.

24
Q

What is the mechanism of action (MOA) of toxicosis from ingestion of Poinsettia plants (primarily seen in cats)?

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A

Topical oral mucosal irritation

(mild and rare)

Large amounts need to be ingested to produce any signs at all.

No gastrointestinal, renal, hepatic, or other effects of clinical significance.

25
What are the **three** **classical histologic findings** in the liver resulting from **pyrrolizidine alkaloid** toxicosis in herbivores?
1. Bridging portal fibrosis 2. Bile duct proliferation 3. Megalocytosis
26
Which **byproduct** of raw bread dough has been associated with **toxicosis** in dogs?
Ethanol ## Footnote Also, the yeast can ferment in the stomach to make the dough enlarge, leading to gastric dilatation/volvulus.
27
What are some **emetics** to consider for **toxicological emergencies** in dogs and cats?
* Dogs: apomorphine, ropinirole, and hydrogen peroxide (less favorable due to risk of gastric ulceration) * Cats: medetomidine, xylazine, hydromorphone ## Footnote Salt is contraindicated in all spp. due to risk of severe hypernatremia if emesis does not occur.
28
A **horse** ingests wilted **red maple** (Acer rubrum) leaves and develops weakness, tachycardia, and dark brown urine. What **type of anemia** is most likely? * A. Iron‑deficiency nonregenerative anemia * B. Thrombocytopathia with spontaneous hemorrhages * C. Intravascular hemolytic anemia with Heinz bodies and methemoglobinemia * D. Aplastic (non-regenerative) anemia due to bone marrow suppression affecting all blood cell lines
C. Acute intravascular hemolytic anemia with Heinz‑body formation and methemoglobinemia ## Footnote Oxidative compounds in wilted red maple leaves damage red blood cells, leading to rapid hemolysis and reduced oxygen‑carrying capacity.
29
A **horse** grazing a pasture in autumn suddenly develops muscle weakness, tremors, dark brown urine, and rapid recumbency. Which **toxin** is most likely responsible for this condition known as **atypical or seasonal pasture myopathy**?
Hypoglycin A, a toxic amino acid found in seeds and seedlings of certain *Acer* spp. trees | (e.g., sycamore and box elder) ## Footnote This toxin disrupts fatty acid metabolism in muscle cells, leading to rapid rhabdomyolysis and release of myoglobin.
30
Give **two** examples of situations when **inducing emesis** is **contraindicated** after a toxic ingestion in animals.
* Animal is comatose or has a significantly depressed mental status * Toxin ingested is corrosive (e.g., strong acids or alkalis) * Animal has a seizure disorder or is actively seizuring * Risk of aspiration (e.g., recent anesthesia or vomiting reflex compromised) * Toxin is a hydrocarbon with high aspiration potential (e.g., gasoline, kerosene) * In horses (cannot vomit)
31
Which **gastrointestinal cathartic** is commonly administered to **horses** via nasogastric tube after toxin ingestion, and why?
Magnesium sulfate, an osmotic cathartic that draws water into the gut lumen, increasing motility and reducing toxin absorption
32
Why are **gastrointestinal toxins** relatively **uncommon** in **ruminants** compared to monogastric species?
The rumen’s microbial fermentation and large volume dilute or detoxify many ingested compounds | (reducing the likelihood of GI toxicosis)
33
What is the most commonly administered **gastrointestinal adsorbent** in veterinary toxicology, and what is its primary **purpose**?
* Activated charcoal * Binds a wide range of toxins in the gastrointestinal tract to reduce systemic absorption
34
Which **class of insecticides** found in canine flea products is especially **toxic to cats**, and why?
Pyrethrins and pyrethroids, because cats lack an effective hepatic glucuronidation pathway needed to metabolize these compounds ## Footnote Pyrethrins/pyrethroids commonly cause GI and CNS toxicity; especially in cats but possible in any veterinary species.
35
A **dog** presents three days after suspected **rodenticide** ingestion with no active bleeding; which **coagulation parameter** is expected to be abnormal first?
Prothrombin time | (PT) ## Footnote Factor VII is depleted first in vitamin K-antagonist rodenticides because it has the shortest half-life of all the vitamin K-dependent factors. Factor VII depletion causes prolongation of the extrinsic pathway first (measured with PT).
36
A dog presents with depression, vomiting, and polyuria/polydipsia after eating a bag of vitamins. Labwork shows marked hypercalcemia, hyperphosphatemia, and azotemia. **Which toxin is most likely involved?**
Cholecalciferol | (vitamin D₃ rodenticide) ## Footnote Vitamin D₃ toxicity increases calcium and phosphorus absorption and mobilization, leading to soft-tissue mineralization and acute kidney injury.
37
A veterinarian is inducing **emesis** in a dog that ingested **zinc phosphide**. What is a major **human health risk** to consider?
Phosphine gas released from vomitus is highly toxic when inhaled, causing respiratory injury, including noncardiogenic pulmonary edema ## Footnote Induce vomiting only in well-ventilated areas or avoid if possible; use extreme caution and PPE when handling animals exposed to zinc phosphide.
38
Match the species with the correct most common clinical signs of **lead toxicosis**. * A. Dogs: Anemia, pallor, petechiation, polyuria/polydipsia * B. Young ruminants: Ataxia, blindness, jaw-chomping, tremors, convulsions * C. Horses: Diarrhea, salivation, hyperexcitability, and ill thrift * D. Birds: Roaring (stridor), dysphagia, chronic weight loss
B. Young ruminants: Ataxia, blindness, jaw-chomping, tremors, convulsions ## Footnote Other species: Dogs – GI upset, hyperexcitability or depression; Horses (chronic exposure) – Roaring (stridor), dysphagia, chronic weight loss, diarrhea; Birds – Anorexia, ataxia, weight loss, anemia
39
Which species are susceptible to **zinc toxicosis**?
All species ## Footnote Can cause GI irritation, hemolysis, and organ injury in any animal, from small animals and foals (especially sensitive) to swine, ruminants, fish, and pet birds.
40
Which **toxin** in **yew plants** is responsible for toxicity, and which **body system** is primarily affected?
* Toxin: Taxine alkaloids * Affected system: Cardiac ## Footnote Taxine alkaloids disrupt normal electrical activity in the heart, causing arrhythmias and sudden death in all veterinary species.
41
A **cat** presents for drooling and mild coughing. The cat's breath has an odor of **hydrocarbon**. Which **rapid test** can help confirm the top differential?
Spot test: mix vomitus or suspect material with water; a positive result is petroleum odor and distillates rising to the surface ## Footnote Hydrocarbons separate on water and release their characteristic odor, providing a quick confirmation of exposure.
42
A dog is rescued from a house fire and presents with coughing, weakness, and bright red mucous membranes. **Which toxin is most likely responsible for these clinical signs?**
Carbon monoxide | (CO) ## Footnote Common sources: smoke from fires, engine exhaust, poorly ventilated gas appliances. CO binds hemoglobin with high affinity, preventing oxygen delivery and causing tissue hypoxia, often with bright red mucous membranes.
43
Name a scenario in which inducing **emesis** in a dog or cat would be **contraindicated**.
* Patients with neurologic deficits (because airway may not be well-protected) * Ingestion of corrosive substances (will cause additional esophageal irritation) * Situations with a high risk of aspiration
44
A **horse** is suspected of ingesting a toxin. Which **cathartic** (given via nasogastric intubation) is recommended to speed gastrointestinal **transit** during enteral decontamination?
Magnesium sulfate - it helps accelerate GI transit in horses, improving toxin clearance | (especially when used with activated charcoal) ## Footnote Remember horses cannot vomit so inducing emesis is not an option.
45
When treating a **ruminant** with **neurologic** signs for possible **toxicosis**, what important safety precaution should always be taken?
Wear gloves and take full protective measures, because rabies must always be considered a rule-out
46
How are **ruminants** most likely exposed to **arsenic**?
By licking or ingesting copper- and arsenic-treated lumber, or from contaminated soil or groundwater ## Footnote Inorganic arsenic exposure in ruminants leads to GI, cardiovascular, and neurologic signs.
47
How can **urea/nonprotein nitrogen** (NPN) toxicosis be **prevented** in **ruminants**?
* Gradually transition cattle to new diets * Limit NPN (e.g., urea) to safe amounts in the ration ## Footnote Sudden intake of high NPN levels can overwhelm rumen microbes, producing toxic ammonia and CNS signs; gradual adaptation prevents hyperammonemia.
48
What organ system is most affected when a **dog** ingests **sago palm**?
The liver | (also GI and neurologic, but liver damage is primary/ life-threatening) ## Footnote Sago palm contains cycasin, a potent hepatotoxin that causes acute liver failure in dogs.
49
What part of the **sago palm** plant has the **highest concentration of toxins**, resulting in the most severe clinical signs?
The seeds ## Footnote Even a single seed can be fatal due to its concentrated toxin load
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