Toxicology

Question 1

What are the toxic properties of hydrogen peroxide?

Answer 1

Corrosive damage - Gastric ulceration
Gas production - Bloat, gas emboli
Oxidative damage - lipid membranes

Question 2

What is intralipid emulsion used for?

Answer 2

Lipophilic drug intoxication

Question 3

What are side-effects to intralipid therapy?

Answer 3

Corneal lipidosis (reversible)

hypertriglyceridemia

Question 4

What are autonomic clinical signs of serotonin syndrome?

Answer 4

CV: Tachycardia, hypertension (BP fluctuating widely)

GI: abdominal pain, hypersalivation, nausea, vomiting

Others: Hyperthermia (can be life-threatening), tachypnea, mydriasis

Question 5

What is the antidote for serotonin syndrome?

Answer 5

Cyproheptadine - non-selective serotonin (5-HT2) receptor antagonist

Question 6

What is the toxic mechanism for inocybe mushrooms?

Answer 6

Muscarine contained within the mushroom - Competes with Ach for receptor

Question 7

What is the treatment for inocybe mushroom toxicity?

Answer 7

Atropine

Question 8

What is the MOA for chocolate toxicity?

Answer 8

Theobromine - Competitive inhibitor of cellular adenosine receptors

Question 9

Which canabinoid receptor is associated with marijuana toxicity?

Answer 9

CB-1

Question 10

What is the main system affected with bromethalin toxicity?

Answer 10

CNS - cerebral and spinal cord edema and increased lipid peroxidation

Question 11

What is the toxic mechanism for bromethalin?

Answer 11

Uncouple oxidative phosphorylation - decreased cellular ATP and failure of Na+/K+ ATPase - Neurons lose osmotic control, retain sodium

Question 12

What is the treatment for bromethalin toxicity?

Answer 12

Decontamination

Intralipid therapy

Question 13

What is the prognosis for bromethalin toxicity?

Answer 13

Poor/grave if neurologic symptoms are present

Question 14

Why are cats more sensitive to pyrethrin toxicity?

Answer 14

More sensitive to toxicity due to the lack of substantial glucuronide conjugation

Question 15

What is the mechanism of action of organophosphates?

Answer 15

Inhibit acetylcholinesterase - Ach accumulates

Some bind irreversibly - Carbamate is reversible

Question 16

What are treatments for organophosphate toxicity?

Answer 16

Atropine - Competitive antagnosit of Ach receptors

2-PAM (Pralidoxime chloride) - Reactivates inactivated cholinesterase

Question 17

Are dogs or cats more susceptible to ethylene glycol toxicity?

Answer 17

Cats

Reported lethal dose (min) = cats 1.4 mL/kg vs dogs 4.4 mL/kg

Question 18

What is the mechanism of toxicity of ethylene glycol?

Answer 18

Ethylene glycol is converted to glycoaldehyde by alcohol dehydrogenase (ADH)

Glycoaldehyde is further metabolized to glycolate, glyoxalate, and oxalate (toxic metabolites)

Calcium oxalate crystals in tubule

Question 19

What causes the acidosis in ethylene glycol toxicity?

Answer 19

Glycolic acid

Question 20

How is ethylene glycol diagnosed?

Answer 20

Wood’s lamp - urine, vomit, muzzle (exposure)

Ethylene glycol test - 1 hour post exposure. Most accurate within 12-24 hours after exposure

Blood test

Question 21

What are medical therapies for ethylene glycol toxicity?

Answer 21

Ethanol - competes with alcohol dehydrogenase

4‐Methylpyrazole, 5% (fomepizole)

Question 22

What are toxins produced by cyanobacteria (general systems)?

Answer 22

Hepatotoxins

Neurotoxins

Question 23

What species is affected with xylotol?

Answer 23

Dogs

Cats not reported

Question 24

How does xylotol cause hypoglycemia?

Answer 24

Causes an increase in blood insulin concentrations

Question 25

What are xylotol's effects on the liver?

Answer 25

Acute hepatic necrosis (unknown mechanism)

Question 26

What is the toxic metabolite of acetaminophen?

Answer 26

NAPQI - Inactivated by gluthatione conjugation

Question 27

How do cats metabolize acetaminophen?

Answer 27

Alternative pathway – deacetylation via hepatic carboxyesterases to produce paraaminophenol (toxic metabolite, RBC oxidative damage) Methemoglobinemia

Question 28

What is the treatment for acetaminophen toxicity in cats?

Answer 28

NAC (cysteine and sulfate source, direct antioxidant effect) Ascorbic acid (30 mg/kg IV Q6 hr.) until resolution of methemoglobinemia

Question 29

Are ibuprofen and naproxen COX selective or non selective?

Answer 29

Non-selective (use both COX 1 and 2)

Question 30

What is the mechanism of toxicity of lead?

Answer 30

Lead competes with calcium ions - substitutes for Ca++ in bone, alters nerve and muscle transmission, displaces Ca++ from calcium binding proteins. Inhibits thiol (‐SH) containing enzymes, interfering with heme synthesis

Question 31

What are clinical signs of lead toxicity?

Answer 31

Anemia with nucleated RBC Gastrointestinal signs CNS - cerebral edema

Question 32

How does calcium EDTA work in the treatment of lead toxicity?

Answer 32

Chelation through displacement Ca++ forming a divalent or trivalent metal complex that is non‐ionic and soluble

Question 33

What are side effects of calcium EDTA?

Answer 33

Nephrotoxic, GI irritant

Question 34

Is penicillamine indicated for GI lead toxicosis?

Answer 34

NO - penicillamine enhances absorption of lead

Question 35

Which pennies can cause zinc toxicity?

Answer 35

Pennies minted after 1982

Question 36

What are the clinical signs of zinc toxicity?

Answer 36

Hemolytic anemia Acute kidney injury

Question 37

What is the toxic principle of pyrethrin?

Answer 37

Binds to sodium channels and prolong conductance

Question 38

What is the mechanism of toxicity of strychnine?

Answer 38

Inhibits glycine - No inhibition

Question 39

What are the clinical signs of strychnine toxicity?

Answer 39

Stiff, tense, tonic extensor rigidity, death-opisthotonos because of paralysis of respiratory muscles

Question 40

What is the toxic principle of cyanide?

Answer 40

Inhibits cytochrome C oxidase - Prevents mitochondrial respiration.

Question 41

What is the antidote for cyanide toxicity?

Answer 41

hydroxycobalamin Nitrates Sodium thiosulfate

Question 42

5-FU toxicity in cats vs dogs

Answer 42

Cats are extremely sensitive to 5-FU - only a few licks can cause life-threatening toxicity (Fatal CNS signs)

Question 43

What is the toxic principle behind 5-FU?

Answer 43

5-FU's metabolite causes failure of the urea cycle - leads to severe ammonia build-up

Question 44

What is a specific therapy for Strychnine?

Answer 44

Acidify the urine - Hastens urinary excretion

Question 45

Ethylene glycol (increases/decreases) osmolarity?

Answer 45

Increases

Question 46

What is a side effect of potassium bromide in cats?

Answer 46

Pneumonitis

Question 47

How do fluoroquinolones affect theophylline metabolism?

Answer 47

Fluoroquinolones inhibit metabolism of theophylline - NEED to decrease the dose of theophylline