Toxicology Flashcards
What are the toxic properties of hydrogen peroxide?
Corrosive damage - Gastric ulceration
Gas production - Bloat, gas emboli
Oxidative damage - lipid membranes
What is intralipid emulsion used for?
Lipophilic drug intoxication
What are side-effects to intralipid therapy?
Corneal lipidosis (reversible)
hypertriglyceridemia
What are autonomic clinical signs of serotonin syndrome?
CV: Tachycardia, hypertension (BP fluctuating widely)
GI: abdominal pain, hypersalivation, nausea, vomiting
Others: Hyperthermia (can be life-threatening), tachypnea, mydriasis
What is the antidote for serotonin syndrome?
Cyproheptadine - non-selective serotonin (5-HT2) receptor antagonist
What is the toxic mechanism for inocybe mushrooms?
Muscarine contained within the mushroom - Competes with Ach for receptor
What is the treatment for inocybe mushroom toxicity?
Atropine
What is the MOA for chocolate toxicity?
Theobromine - Competitive inhibitor of cellular adenosine receptors
Which canabinoid receptor is associated with marijuana toxicity?
CB-1
What is the main system affected with bromethalin toxicity?
CNS - cerebral and spinal cord edema and increased lipid peroxidation
What is the toxic mechanism for bromethalin?
Uncouple oxidative phosphorylation - decreased cellular ATP and failure of Na+/K+ ATPase - Neurons lose osmotic control, retain sodium
What is the treatment for bromethalin toxicity?
Decontamination
Intralipid therapy
What is the prognosis for bromethalin toxicity?
Poor/grave if neurologic symptoms are present
Why are cats more sensitive to pyrethrin toxicity?
More sensitive to toxicity due to the lack of substantial glucuronide conjugation
What is the mechanism of action of organophosphates?
Inhibit acetylcholinesterase - Ach accumulates
Some bind irreversibly - Carbamate is reversible
What are treatments for organophosphate toxicity?
Atropine - Competitive antagnosit of Ach receptors
2-PAM (Pralidoxime chloride) - Reactivates inactivated cholinesterase
Are dogs or cats more susceptible to ethylene glycol toxicity?
Cats
Reported lethal dose (min) = cats 1.4 mL/kg vs dogs 4.4 mL/kg
What is the mechanism of toxicity of ethylene glycol?
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
What causes the acidosis in ethylene glycol toxicity?
Glycolic acid
How is ethylene glycol diagnosed?
Wood’s lamp - urine, vomit, muzzle (exposure)
Ethylene glycol test - 1 hour post exposure. Most accurate within 12-24 hours after exposure
Blood test
What are medical therapies for ethylene glycol toxicity?
Ethanol - competes with alcohol dehydrogenase
4‐Methylpyrazole, 5% (fomepizole)
What are toxins produced by cyanobacteria (general systems)?
Hepatotoxins
Neurotoxins
What species is affected with xylotol?
Dogs
Cats not reported
How does xylotol cause hypoglycemia?
Causes an increase in blood insulin concentrations
What are xylotol’s effects on the liver?
Acute hepatic necrosis (unknown mechanism)
What is the toxic metabolite of acetaminophen?
NAPQI - Inactivated by gluthatione conjugation
How do cats metabolize acetaminophen?
Alternative pathway – deacetylation via hepatic carboxyesterases to produce paraaminophenol
(toxic metabolite, RBC oxidative damage)
Methemoglobinemia
What is the treatment for acetaminophen toxicity in cats?
NAC (cysteine and sulfate source, direct antioxidant effect)
Ascorbic acid (30 mg/kg IV Q6 hr.) until resolution of methemoglobinemia
Are ibuprofen and naproxen COX selective or non selective?
Non-selective (use both COX 1 and 2)
What is the mechanism of toxicity of lead?
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
What are clinical signs of lead toxicity?
Anemia with nucleated RBC
Gastrointestinal signs
CNS - cerebral edema
How does calcium EDTA work in the treatment of lead toxicity?
Chelation through displacement Ca++ forming a divalent or trivalent metal complex that is
non‐ionic and soluble
What are side effects of calcium EDTA?
Nephrotoxic, GI irritant
Is penicillamine indicated for GI lead toxicosis?
NO - penicillamine enhances absorption of lead
Which pennies can cause zinc toxicity?
Pennies minted after 1982
What are the clinical signs of zinc toxicity?
Hemolytic anemia
Acute kidney injury
What is the toxic principle of pyrethrin?
Binds to sodium channels and prolong conductance
What is the mechanism of toxicity of strychnine?
Inhibits glycine - No inhibition
What are the clinical signs of strychnine toxicity?
Stiff, tense, tonic extensor rigidity, death-opisthotonos because of paralysis of respiratory muscles
What is the toxic principle of cyanide?
Inhibits cytochrome C oxidase - Prevents mitochondrial respiration.
What is the antidote for cyanide toxicity?
hydroxycobalamin
Nitrates
Sodium thiosulfate
5-FU toxicity in cats vs dogs
Cats are extremely sensitive to 5-FU - only a few licks can cause life-threatening toxicity (Fatal CNS signs)
What is the toxic principle behind 5-FU?
5-FU’s metabolite causes failure of the urea cycle - leads to severe ammonia build-up
What is a specific therapy for Strychnine?
Acidify the urine - Hastens urinary excretion
Ethylene glycol (increases/decreases) osmolarity?
Increases
What is a side effect of potassium bromide in cats?
Pneumonitis
How do fluoroquinolones affect theophylline metabolism?
Fluoroquinolones inhibit metabolism of theophylline - NEED to decrease the dose of theophylline
