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ABVT practice questions

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Question 1Veterinary Toxicology

Which antidote is the specific treatment for acetaminophen (paracetamol) toxicosis in dogs and cats?

  1. Atropine sulfate
  2. N-acetylcysteine Correct answer.
  3. Methylene blue
  4. Pralidoxime chloride

Explanation

Acetaminophen is metabolized to a reactive intermediate that depletes glutathione and oxidizes hemoglobin; N-acetylcysteine replenishes hepatic glutathione and is the specific antidote. Supportive care alone does not prevent hepatic necrosis or methemoglobinemia.

Question 2Veterinary Toxicology

Which clinical sign is most characteristic of anticoagulant rodenticide (e.g., brodifacoum) poisoning in a dog?

  1. Acute renal failure with tubular casts
  2. Photosensitization of unpigmented skin
  3. Cholinergic signs such as salivation and miosis
  4. Hemorrhage from mucosal surfaces and body cavities Correct answer.

Explanation

Anticoagulant rodenticides inhibit vitamin K epoxide reductase, depleting active clotting factors II, VII, IX and X, so animals bleed from gums, nose, and into cavities. Coagulopathy rather than renal or cholinergic injury defines the syndrome.

Question 3Veterinary Toxicology

A dog that ate chocolate is at greatest risk of which toxic effect?

  1. Coagulopathy from vitamin K antagonism
  2. Hypoglycemia from insulin excess
  3. Hemolysis from oxidant damage
  4. Tachyarrhythmia and CNS stimulation from methylxanthines Correct answer.

Explanation

Chocolate contains theobromine and caffeine, methylxanthines that increase intracellular calcium and catecholamine effects, producing tachycardia, arrhythmias, tremors and seizures. Oxidant hemolysis and coagulopathy are not features of methylxanthine toxicosis.

Question 4Veterinary Toxicology

Xylitol ingestion in dogs most commonly causes which acute metabolic derangement?

  1. Hypercalcemia from bone resorption
  2. Hypoglycemia from insulin release Correct answer.
  3. Hypernatremia from free water loss
  4. Hyperkalemia from rhabdomyolysis

Explanation

Xylitol strongly stimulates insulin secretion in dogs, causing profound hypoglycemia within 30 to 60 minutes; higher doses can also cause hepatic necrosis. Electrolyte disturbances such as hyperkalemia or hypercalcemia are not the primary effect.

Question 5Veterinary Toxicology

Which plant is classically associated with acute cyanide poisoning in grazing livestock?

  1. Solanum species (nightshade)
  2. Nerium oleander
  3. Prunus species (cherry, chokecherry) Correct answer.
  4. Taxus species (yew)

Explanation

Prunus leaves and pits contain cyanogenic glycosides that release hydrogen cyanide when damaged, blocking cytochrome oxidase and causing rapid death. The other plants listed cause different toxic syndromes.

Question 6Veterinary Toxicology

Which clinical sign is most consistent with organophosphate insecticide poisoning?

  1. Jaundice and photosensitization
  2. Mydriasis, dry mucous membranes, and tachycardia
  3. Polyuria and glycosuria
  4. Miosis, salivation, and bradycardia Correct answer.

Explanation

Organophosphates inhibit acetylcholinesterase, allowing acetylcholine accumulation and producing muscarinic signs such as miosis, salivation, lacrimation, and bradycardia, plus nicotinic and CNS signs. Anticholinergic signs are the opposite of this pattern.

Question 7Veterinary Toxicology

Which vitamin K form is appropriate for treating anticoagulant rodenticide poisoning?

  1. Vitamin K1 (phytonadione) Correct answer.
  2. Vitamin K4 (menadiol)
  3. Vitamin K3 (menadione)
  4. Vitamin K2 (menaquinone)

Explanation

Vitamin K1 (phytonadione) bypasses the inhibited epoxide reductase and restores clotting factor synthesis; it is the accepted antidote. Menadione and related synthetic forms are ineffective and can cause oxidative injury.

Question 8Veterinary Toxicology

Which route of exposure most often causes lead poisoning in pet birds?

  1. Inhalation of lead dust from bedding
  2. Dermal absorption from painted perches
  3. Ingestion of lead-containing objects such as weights or solder Correct answer.
  4. Absorption through the drinking water only

Explanation

Birds commonly ingest lead shot, fishing weights, curtain weights, or solder, and the acidic proventriculus enhances absorption, causing neurologic and gastrointestinal signs. Inhalation, dermal absorption, and water-only exposure are not the typical routes.

Question 9Veterinary Toxicology

A cat presents with methemoglobinemia and Heinz body anemia after ingesting a topical product. Which exposure is most likely responsible?

  1. Fipronil spray
  2. Ivermectin paste
  3. Benzocaine-containing topical cream Correct answer.
  4. Permethrin spot-on formulated for dogs

Explanation

Benzocaine and other local anesthetics oxidize feline hemoglobin, producing methemoglobinemia and Heinz bodies. Permethrin causes tremors and seizures, and fipronil or ivermectin cause neurologic signs but not oxidant hemolysis.

Question 10Veterinary Toxicology

A dog ingested ethylene glycol several hours ago and now shows ataxia and increased drinking. Which therapy is most appropriate?

  1. Activated charcoal to bind the parent compound
  2. Fomepizole or ethanol to block alcohol dehydrogenase Correct answer.
  3. Naloxone to reverse opioid effects
  4. Sodium bicarbonate alone to alkalinize urine

Explanation

Ethylene glycol is metabolized by alcohol dehydrogenase to toxic acid metabolites; fomepizole (or ethanol) competitively inhibits this enzyme and prevents metabolite formation. Charcoal poorly adsorbs the glycol, and alkalinization alone does not stop metabolism.

Question 11Veterinary Toxicology

Which mechanism explains the toxicity of cholecalciferol rodenticides?

  1. Oxidation of hemoglobin to methemoglobin
  2. Blockade of acetylcholinesterase causing cholinergic signs
  3. Excess vitamin D activity causing hypercalcemia and tissue mineralization Correct answer.
  4. Inhibition of vitamin K epoxide reductase causing hemorrhage

Explanation

Cholecalciferol raises serum calcium by increasing intestinal absorption and bone resorption, leading to soft-tissue mineralization, renal failure, and cardiac arrhythmias. The other mechanisms describe unrelated rodenticides or toxins.

Question 12Veterinary Toxicology

A dog presents with hemolytic anemia and hemoglobinuria after eating a large quantity of onions. Which mechanism best explains this?

  1. Direct inhibition of bone marrow erythropoiesis
  2. Oxidative damage to hemoglobin forming Heinz bodies Correct answer.
  3. Splenic sequestration from portal hypertension
  4. Immune-mediated destruction triggered by plant lectins

Explanation

Onion and garlic contain organosulfur compounds that oxidize hemoglobin, forming Heinz bodies and leading to hemolysis. The effect is oxidative rather than immune-mediated or due to marrow suppression.

Question 13Veterinary Toxicology

Which finding on history and examination most supports a diagnosis of metaldehyde (slug bait) poisoning in a dog?

  1. Mydriasis with dry mucous membranes
  2. Oliguria with calcium oxalate crystals
  3. Icterus and prolonged clotting times
  4. Acute tremors, hyperthermia, and seizures after garden exposure Correct answer.

Explanation

Metaldehyde is a neurotoxin that causes muscle tremors, hyperthermia, and seizures, often after exposure in gardens. Jaundice, oxalate crystalluria, and anticholinergic signs reflect other toxicoses.

Question 14Veterinary Toxicology

A dog that scavenged from a landfill develops severe salivation, muscle fasciculations, and miosis. Which treatment combination is most appropriate?

  1. Atropine for muscarinic signs plus pralidoxime to reactivate cholinesterase Correct answer.
  2. Vitamin K1 plus plasma transfusion
  3. Fomepizole plus sodium bicarbonate
  4. Naloxone plus fluid diuresis

Explanation

These signs indicate organophosphate or carbamate cholinesterase inhibition; atropine controls muscarinic effects while pralidoxime reactivates phosphorylated enzyme in organophosphate (not carbamate) cases. The other combinations target unrelated toxicoses.

Question 15Veterinary Toxicology

Which laboratory finding is expected in a dog with zinc toxicosis from ingested pennies?

  1. Metabolic alkalosis with hypochloremia
  2. Intravascular hemolysis with Heinz bodies Correct answer.
  3. Prolonged prothrombin time
  4. Marked hypercalcemia

Explanation

Zinc dissolves in gastric acid and causes oxidative hemolysis with Heinz body formation and hemoglobinuria. Coagulopathy, alkalosis, and hypercalcemia are not characteristic of zinc toxicosis.

Question 16Veterinary Toxicology

A dog is presented after ingesting a macadamia nut product. Which expected clinical picture best fits this exposure?

  1. Hindlimb weakness, tremors, and hyperthermia that usually resolve with supportive care Correct answer.
  2. Acute hepatic failure with prolonged clotting times
  3. Methemoglobinemia requiring methylene blue
  4. Severe hemorrhagic gastroenteritis progressing to sepsis

Explanation

Macadamia nut toxicosis in dogs produces weakness, tremors, and hyperthermia that generally resolve within 24 to 48 hours with supportive care. It does not cause hepatic failure, sepsis, or methemoglobinemia.

Question 17Veterinary Toxicology

Which mechanism underlies grayanotoxin toxicity from ingestion of certain rhododendron or mountain laurel plants?

  1. Inhibition of the sodium-potassium ATPase pump
  2. Blockade of voltage-gated potassium channels
  3. Irreversible antagonism of GABA-A receptors
  4. Persistent activation of voltage-gated sodium channels Correct answer.

Explanation

Grayanotoxins bind voltage-gated sodium channels and prevent inactivation, causing prolonged depolarization with bradycardia, hypotension, and gastrointestinal signs. Potassium channel blockade, ATPase inhibition, and GABA antagonism describe other toxins.

Question 18Veterinary Toxicology

A horse grazes on pasture containing bracken fern and later shows bleeding and weakness. Which hematologic abnormality is most consistent?

  1. Isolated thrombocytosis
  2. Pancytopenia from bone marrow suppression Correct answer.
  3. Hyperfibrinogenemia from chronic inflammation
  4. Eosinophilia from allergic reaction

Explanation

Bracken fern contains ptaquiloside and thiaminase-related compounds; chronic ingestion in ruminants and horses causes bone marrow suppression with pancytopenia and bleeding. Thrombocytosis, eosinophilia, and hyperfibrinogenemia are not the hallmark.

Question 19Veterinary Toxicology

Which is the most appropriate initial decontamination measure for a dog that ingested a toxin within the past 30 minutes and is alert?

  1. Perform immediate gastric lavage in all cases
  2. Induce emesis with apomorphine or hydrogen peroxide under veterinary direction Correct answer.
  3. Give intravenous lipid emulsion as first-line therapy
  4. Administer activated charcoal without assessing airway protection

Explanation

Early emesis induction can remove recently ingested toxin in an alert animal, with drug choice depending on species and condition. Lavage, charcoal, and lipid emulsion are reserved for specific situations based on risk and airway safety.

Question 20Veterinary Toxicology

Which mechanism explains the toxicity of strychnine?

  1. Irreversible inhibition of acetylcholinesterase
  2. Depletion of hepatic glutathione
  3. Blockade of cardiac sodium channels
  4. Competitive antagonism of glycine receptors in the spinal cord Correct answer.

Explanation

Strychnine antagonizes glycine, the inhibitory neurotransmitter in the spinal cord, producing tetanic convulsions with intact consciousness. Cholinesterase inhibition, sodium channel blockade, and glutathione depletion describe other toxins.

Question 21Veterinary Toxicology

A dog with a history of ingesting a large amount of raisins presents with vomiting and azotemia. Which pathophysiologic process best explains the renal injury?

  1. Hemoglobin-induced tubular obstruction only
  2. Immune complex glomerulonephritis
  3. Acute tubular necrosis from an unidentified nephrotoxic component Correct answer.
  4. Calcium oxalate crystal precipitation in tubules

Explanation

Grape and raisin toxicosis in dogs causes acute kidney injury consistent with proximal tubular necrosis, though the precise toxin remains unidentified. Oxalate crystals, pure pigment obstruction, and immune complex disease are not the accepted mechanism.

Question 22Veterinary Toxicology

Which statement best describes the toxicologic significance of theobromine's long half-life in dogs?

  1. A single dose of activated charcoal is always sufficient
  2. Clinical signs and cardiac effects can persist for many hours, requiring prolonged monitoring Correct answer.
  3. Theobromine is not absorbed from the gastrointestinal tract
  4. Signs resolve within one hour of ingestion

Explanation

Dogs eliminate theobromine slowly, so methylxanthine effects such as tachycardia and tremors can persist for 12 to 72 hours and require extended monitoring and repeated charcoal dosing. Rapid resolution and lack of absorption are incorrect.

Question 23Veterinary Toxicology

A cat with permethrin toxicosis is tremoring. Which consideration is most important when choosing therapy?

  1. Methylene blue is the antidote of choice
  2. Atropine reverses the tremors
  3. Cats lack efficient glucuronidation, so lipid-soluble pyrethroids clear slowly and require prolonged supportive care Correct answer.
  4. Cats rapidly metabolize pyrethroids, so signs are brief

Explanation

Cats have limited glucuronidation capacity, prolonging pyrethroid exposure and neurologic signs, so treatment relies on decontamination, seizure control, and supportive care. Rapid metabolism, methylene blue, and atropine are not applicable.

Question 24Veterinary Toxicology

Which scenario most strongly suggests a diagnosis of botulism rather than tick paralysis in a dog?

  1. Acute ascending paralysis with ticks found on the head and neck
  2. Sudden onset of seizures with normal mentation between episodes
  3. Hemorrhagic diarrhea with thrombocytopenia
  4. Ascending flaccid paralysis with normal sensation after eating spoiled carcass material Correct answer.

Explanation

Botulism follows ingestion of preformed toxin in spoiled material and causes ascending flaccid paralysis with intact sensation, whereas tick paralysis typically improves after tick removal. Seizures and thrombocytopenia are not features of either condition.

Question 25Veterinary Toxicology

A dog ingested a sustained-release iron supplement. Which finding best indicates serious iron toxicosis requiring aggressive therapy?

  1. Mild self-limiting diarrhea with normal acid-base status
  2. Isolated hypernatremia
  3. Persistent vomiting with metabolic acidosis and serum iron in the toxic range Correct answer.
  4. Transient pica without gastrointestinal signs

Explanation

Severe iron toxicosis causes hemorrhagic gastroenteritis, metabolic acidosis, and shock, and serum iron concentrations above the toxic threshold warrant chelation with deferoxamine. Mild or absent signs and isolated electrolyte changes do not indicate serious poisoning.

Question 26Veterinary Toxicology

Which activated charcoal dosing regimen is most appropriate for a dog with recent ingestion of a non-corrosive toxin?

  1. 5 g/kg given intravenously
  2. 1–3 g/kg mixed with water as a slurry Correct answer.
  3. 0.1 g/kg mixed with a cathartic
  4. 10–20 g/kg given as dry powder

Explanation

Activated charcoal is typically given orally as a slurry at 1–3 g/kg (or roughly 1–3 g/kg) in dogs to adsorb toxins. Higher doses risk constipation or obstruction, and dry powder or IV routes are inappropriate and dangerous.

Question 27Veterinary Toxicology

Which clinical sign is most characteristic of selective serotonin reuptake inhibitor (SSRI) overdose in a dog?

  1. Icterus and coagulopathy
  2. Tremors, hyperthermia, and mydriasis Correct answer.
  3. Polyuria and polydipsia
  4. Sedation and bradycardia

Explanation

SSRI toxicity in dogs often produces serotonin syndrome-like signs: tremors, hyperthermia, mydriasis, and agitation. Sedation, polyuria, and hepatic signs are less typical.

Question 28Veterinary Toxicology

Which plant is most commonly associated with causing contact dermatitis in animals?

  1. Oleander (Nerium oleander)
  2. Poinsettia (Euphorbia pulcherrima) Correct answer.
  3. Lily of the valley (Convallaria majalis)
  4. Foxglove (Digitalis purpurea)

Explanation

Poinsettia sap contains diterpene esters that can cause contact dermatitis and gastrointestinal irritation. Oleander, foxglove, and lily of the valley are cardiotoxic plants.

Question 29Veterinary Toxicology

Which clinical sign is most typical of acute boron (boric acid) poisoning in a dog?

  1. Icterus and hepatic failure
  2. Seizures and coma
  3. Vomiting and diarrhea Correct answer.
  4. Hematuria and coagulopathy

Explanation

Acute boric acid ingestion commonly causes gastrointestinal upset such as vomiting and diarrhea. Neurologic and hemorrhagic signs are less typical.

Question 30Veterinary Toxicology

Which clinical sign is most consistent with acute caffeine poisoning in a dog?

  1. Bradycardia and hypothermia
  2. Constipation and bradycardia
  3. Hyperactivity and tachycardia Correct answer.
  4. Polyuria and polydipsia

Explanation

Caffeine is a methylxanthine that stimulates the central nervous system and cardiovascular system, causing hyperactivity, tachycardia, and tremors. Bradycardia and hypothermia are not typical.

Question 31Veterinary Toxicology

Which clinical sign is most characteristic of pyrethrin/pyrethroid toxicity in a cat?

  1. Tremors and hypersalivation Correct answer.
  2. Icterus and coagulopathy
  3. Polyuria and polydipsia
  4. Bradycardia and hypotension

Explanation

Pyrethroids cause neurotoxicity in cats, often presenting with tremors, hypersalivation, and agitation. Bradycardia, icterus, and polyuria are not typical.

Question 32Veterinary Toxicology

Which decontamination method is appropriate for a dog with dermal exposure to a toxic substance?

  1. Administering activated charcoal orally
  2. Inducing emesis with hydrogen peroxide
  3. Providing intravenous fluids only
  4. Bathing with a mild detergent and lukewarm water Correct answer.

Explanation

For dermal exposure, the goal is to remove the substance from the skin by bathing with a mild detergent and lukewarm water. Emesis and activated charcoal are for oral exposures and are not effective for dermal contamination.

Question 33Veterinary Toxicology

Which clinical sign is most suggestive of acute zinc phosphide poisoning in a dog?

  1. Polyuria and polydipsia
  2. Vomiting and abdominal pain Correct answer.
  3. Hematuria and epistaxis
  4. Icterus and hepatic encephalopathy

Explanation

Zinc phosphide reacts with gastric acid to release phosphine gas, causing severe gastrointestinal irritation with vomiting and abdominal pain. Hematuria, icterus, and polyuria are not typical.

Question 34Veterinary Toxicology

Which finding on history is most consistent with acetaminophen toxicity in a cat?

  1. Polyuria and polydipsia
  2. Bradycardia and hypotension
  3. Facial edema and cyanosis Correct answer.
  4. Icterus and coagulopathy

Explanation

Cats are deficient in glucuronidation and are highly sensitive to acetaminophen, which causes methemoglobinemia and Heinz body anemia; facial edema and cyanosis can be seen. Icterus, polyuria, and bradycardia are not typical.

Question 35Veterinary Toxicology

A dog ingested a large amount of chocolate. Which factor most influences the severity of theobromine toxicosis?

  1. The time of day of ingestion
  2. The dog's sex
  3. The dog's age
  4. The type of chocolate (dark vs. milk) Correct answer.

Explanation

Theobromine concentration varies greatly among chocolate types; dark and baking chocolate contain much higher levels than milk chocolate, so the type of chocolate is a major determinant of toxicity. Age, sex, and time of day are less important.

Question 36Veterinary Toxicology

A dog presents with severe hypoglycemia after ingesting a sulfonylurea antidiabetic medication. Which mechanism explains this effect?

  1. Inhibition of insulin degradation in the liver
  2. Direct destruction of pancreatic alpha cells
  3. Stimulation of insulin release from pancreatic beta cells Correct answer.
  4. Increased insulin receptor sensitivity

Explanation

Sulfonylureas close ATP-sensitive potassium channels on pancreatic beta cells, causing insulin release and hypoglycemia. They do not inhibit insulin degradation, increase receptor sensitivity, or destroy alpha cells.

Question 37Veterinary Toxicology

A dog ingested a large amount of grapes. Which pathophysiologic mechanism best explains the resulting acute kidney injury?

  1. Obstruction of renal tubules by crystals
  2. Direct renal tubular toxicity Correct answer.
  3. Immune-mediated glomerulonephritis
  4. Renal ischemia from vasoconstriction

Explanation

Grape and raisin toxicity in dogs is believed to cause direct renal tubular damage, leading to acute kidney injury. Vasoconstriction, crystal obstruction, and immune-mediated glomerulonephritis are not the primary mechanisms.

Question 38Veterinary Toxicology

Which treatment is most appropriate for a dog with severe methemoglobinemia from acetaminophen toxicity?

  1. Methylene blue Correct answer.
  2. N-acetylcysteine
  3. Vitamin K1
  4. Atropine

Explanation

Methylene blue is used to reduce methemoglobin to hemoglobin in cases of methemoglobinemia, including acetaminophen toxicity in dogs. N-acetylcysteine is a hepatoprotectant but does not directly reduce methemoglobin; vitamin K1 and atropine are for other toxicoses.

Question 39Veterinary Toxicology

A cat presents with seizures after ingesting a topical flea product containing permethrin. Which medication is most appropriate for controlling the seizures?

  1. Atropine
  2. Diazepam Correct answer.
  3. Vitamin K1
  4. Naloxone

Explanation

Benzodiazepines such as diazepam are first-line for seizure control in permethrin toxicosis. Atropine, naloxone, and vitamin K1 do not control seizures.

Question 40Veterinary Toxicology

Which laboratory finding is most characteristic of lead poisoning in a dog?

  1. Heinz bodies
  2. Methemoglobinemia
  3. Basophilic stippling of erythrocytes Correct answer.
  4. Hypoglycemia

Explanation

Lead toxicity inhibits heme synthesis and can cause basophilic stippling of red blood cells. Heinz bodies, methemoglobinemia, and hypoglycemia are not typical of lead poisoning.

Question 41Veterinary Toxicology

A dog ingested a macadamia nut product. Which clinical sign is most commonly expected?

  1. Icterus
  2. Hind limb weakness Correct answer.
  3. Bradycardia
  4. Hematuria

Explanation

Macadamia nut toxicity in dogs typically causes hind limb weakness, tremors, and hyperthermia. Hematuria, icterus, and bradycardia are not typical.

Question 42Veterinary Toxicology

A dog ingested a large amount of onions. Which mechanism best explains the resulting hemolytic anemia?

  1. Direct bone marrow suppression
  2. Complement activation
  3. Oxidative damage to hemoglobin Correct answer.
  4. Immune-mediated destruction of red cells

Explanation

Onions contain oxidants that damage hemoglobin, leading to Heinz body formation and hemolysis. Immune-mediated destruction, bone marrow suppression, and complement activation are not the primary mechanisms.

Question 43Veterinary Toxicology

A dog presents with severe salivation, miosis, and muscle fasciculations after exposure to an organophosphate. Which drug is most appropriate to counteract the muscarinic effects?

  1. Naloxone
  2. Pralidoxime
  3. Diazepam
  4. Atropine Correct answer.

Explanation

Atropine is an antimuscarinic that blocks the muscarinic effects (salivation, miosis, bradycardia) of organophosphate toxicity. Pralidoxime reactivates cholinesterase but does not directly block muscarinic receptors; diazepam and naloxone are not indicated for muscarinic signs.

Question 44Veterinary Toxicology

A dog with a history of ingesting a large amount of raisins presents with vomiting and azotemia. Which pathophysiologic mechanism best explains the azotemia?

  1. Postrenal obstruction
  2. Glomerular immune complex deposition
  3. Prerenal azotemia from dehydration
  4. Acute tubular necrosis Correct answer.

Explanation

Raisin toxicity causes acute tubular necrosis leading to intrinsic acute kidney injury and azotemia. Prerenal azotemia from dehydration may occur but is not the primary mechanism; postrenal obstruction and immune complex deposition are not typical.

Question 45Veterinary Toxicology

Which statement best describes the toxicologic significance of the long half-life of theobromine in dogs?

  1. It increases renal excretion
  2. It prevents absorption
  3. It allows accumulation with repeated exposures Correct answer.
  4. It reduces the risk of toxicity

Explanation

The long half-life of theobromine in dogs means it is cleared slowly, so repeated ingestions can lead to accumulation and prolonged toxicity. It does not reduce toxicity, increase excretion, or prevent absorption.

Question 46Veterinary Toxicology

Which scenario most strongly suggests botulism rather than tick paralysis in a dog?

  1. Fever and ticks found on the body
  2. Acute ascending flaccid paralysis with normal mentation Correct answer.
  3. Asymmetric limb weakness
  4. Hypersalivation and miosis

Explanation

Botulism typically causes acute ascending flaccid paralysis with normal mentation and no fever, often after ingestion of spoiled food. Tick paralysis is associated with ticks and may cause ascending paralysis but usually without fever; asymmetric weakness and cholinergic signs are not typical of either.

Question 47Veterinary Toxicology

A dog ingested a sustained-release iron supplement. Which finding best indicates serious iron toxicosis requiring aggressive treatment?

  1. Mild vomiting only
  2. Serum iron level within normal limits
  3. Transient diarrhea without dehydration
  4. Hemorrhagic gastroenteritis and shock Correct answer.

Explanation

Severe iron toxicosis causes hemorrhagic gastroenteritis, shock, and hepatic necrosis. Mild vomiting or transient diarrhea alone may not indicate severe toxicity, and a normal serum iron level suggests low risk.

Question 48Veterinary Toxicology

Which mechanism explains the toxicity of grayanotoxins from ingestion of certain rhododendron plants?

  1. Cholinesterase inhibition
  2. Calcium channel blockade
  3. Sodium channel activation Correct answer.
  4. Potassium channel blockade

Explanation

Grayanotoxins bind to voltage-gated sodium channels, preventing inactivation and causing prolonged depolarization. This leads to gastrointestinal and cardiac signs. Potassium channel blockade, calcium channel blockade, and cholinesterase inhibition are not the mechanisms.

Question 49Veterinary Toxicology

A horse grazes on pasture containing bracken fern and later shows bleeding and weakness. Which hematologic abnormality is most likely?

  1. Thrombocytopenia Correct answer.
  2. Methemoglobinemia
  3. Anemia with Heinz bodies
  4. Eosinophilia

Explanation

Bracken fern contains ptaquiloside and can cause bone marrow suppression, leading to thrombocytopenia and bleeding. Heinz bodies, methemoglobinemia, and eosinophilia are not typical.

Question 50Veterinary Toxicology

Which statement best describes the role of N-acetylcysteine in acetaminophen toxicity in dogs?

  1. It directly reduces methemoglobin to hemoglobin
  2. It blocks opioid receptors
  3. It replenishes glutathione and detoxifies reactive metabolites Correct answer.
  4. It enhances renal excretion of acetaminophen

Explanation

N-acetylcysteine provides cysteine, a precursor for glutathione synthesis, which helps detoxify the reactive metabolite NAPQI. It does not directly reduce methemoglobin, block opioid receptors, or primarily enhance renal excretion.