Ethylene Glycol/Propylene Glycol/Ethanol-Methanol

Question 1

Main use of ethylene glycol

Answer 1

antifreeze

Question 2

Main source of exposure of ethylene glycol

Answer 2

ingestion of antifreeze

Question 3

Toxicokinetics of ethylene glycol

Answer 3

rapidly absorbed from GIT - delayed by food
rapidly distributed to all tissues including CNS
metabolized to toxic metabolites in the liver
oxidized by alcohol dehydrogenase to glycoaldehyde –> oxidized by aldehyde dehydrogenase to glycol acid –> oxidized by aldehyde dehydrogenase to glycoxylic acid, glycine, formic acid, hippuric acid and benzoic acid
oxalic acid binds to serum calcium to form insoluble calcium oxalate crystals (monohydrate) and hypocalcemia

Question 4

MoA of ethylene glycol toxicity

Answer 4

ethylene glycol - direct GI irritation, increased serum osmolality (osmotic diuresis), CNS depression
toxic metabolites - cause metabolic acidosis and acute renal failure

Question 5

Ethylene glycol and acute renal failure

Answer 5

metabolites are cytotoxic to renal tubular epithelium
calcium oxalate monohydrate crystal formation within renal tubules contributes to damage
crystals adhere to cellular membranes, internalized by cell and alter cellular structure and function, increase reactive oxygen species and produce mitochondrial dysfunction

Question 6

Early signs of ethylene glycol toxicosis

Answer 6

EG effects and systemic acidosis
nausea, anorexia, CNS depression, ataxia, incoordination, hypothermia, muscle fasciculations, tachycardia, tachypnea, PU/PD, dehydration, coma, death

Question 7

T/F: cats with ethylene glycol toxicity usually show polydipsia

Answer 7

false

Question 8

Late signs of ethylene glycol toxicosis

Answer 8

oliguric renal failure

vomiting, anorexia, depression, severe lethargy, coma, seizures, oliguria, renal pain

Question 9

Ethylene glycol lesions

Answer 9

Gross - hemorrhagic gastroenteritis, pulmonary edema, pale and swollen kidneys with grey or yellow streaks
Microscopic - yellow birefringent rosette shaped calcium oxalate crystals in the kidney or urine

Question 10

Lab diagnosis of ethylene glycol toxicosis

Answer 10

large anion gap, increased serum osmolality
hypocalcemia, hyperglycaemia, acute renal failure changes
increased PCV and total protein
calcium oxalate crystals in urine sediment

Question 11

causes false positive on a KaceyTM EG test

Answer 11

ethanol, propylene glycol, mannitol, sorbitol, glycerol

Question 12

T/F: Catachem ethylene glycol test can be falsely positive due to ethanol

Answer 12

false

Question 13

Treatment of ethylene glycol toxicity

Answer 13

detoxifcation
specific antidote - inhibitors of alcohol dehydrogenase
fomepizole (best)
ethanol 20% - higher affinity for alcohol dehydrogenase than EG
supportive therapy - sodium bicarb for acidosis
fluid therapy - IV 5% dextrose in half strength saline

Question 14

T/F: dogs and cats are commonly intoxicated by ethanol/methanol

Answer 14

false, its rare

Question 15

T/F a diet with a very high glucose level (18-60%) can cause ethanol toxicosis

Answer 15

true, due to yeast fermentation inGIT

Question 16

Toxicokinetics of ethanol/methanol toxicity

Answer 16

readily absorbed orally, food in stomach delays absorption
widely distributed to CNS
ethanol metabolized by hepatic alcohol dehydrogenase to acetaldehyde –> acetate –> acetyl CoA –> CO2 and water

Question 17

MoA of ethanol/methanol toxicity

Answer 17

irritates mucus membranes
CNS depression
acetaldehyde is vasodilator and induces vomiting
acetate causes metabolic acidosis
ethanol inhibits ADH causing diuresis

Question 18

Signs of acute ethanol/methanol toxicosis

Answer 18

Rapid onset of CNS depression
abnormal behaviour
vomiting
hypothermia, tremor and ataxia
congested MM
PU/PD
death from resp failure

Question 19

Lesions associated with ethanol/methanol toxicosis

Answer 19

congestion of GI mucosa, liver, kidney and lungs

Question 20

Treatment for ethanol/methanol toxicosis

Answer 20

no specific antidote for ethanol, ethanol and fomepizole for methanol
emetics if recent ingestion
activated charcoal not effective
supportive and symptomatic therapy

Question 21

Main use of propylene glycol

Answer 21

antifreeze (“safe”)

Question 22

source of exposure of propylene glycol

Answer 22

accidental ingestion in small animals

giving instead of mineral oil in horses

Question 23

Toxicity of propylene glycol

Answer 23

dogs, cats, cattle and horses susceptible
cats more sensitive
safer than ethylene glycol

Question 24

Toxicokinetics of propylene glyco

Answer 24

rapidly absorbed from GIT and inhalation

metabolized in liver by alcohol dehydrogenase to lactaldehyde –> lactic acid (D and L isomers) –> pyruvic acid

Question 25

Which of the following is FALSE regarding the toxicokinetics of propylene glycol?
A) High concentrations of D-lactic acid may cause lactic acidosis
B) L-lactic acid is used by the TCA cycle
C) propylene glycol is partly excreted in the urine
D) propylene glycol is metabolized in the blood

Answer 25

D - propylene glycol is metabolized in the liver

Question 26

MoA of propylene glycol

Answer 26

not metabolized to toxic metabolites 
osmotic diuresis
CNS depression
D-lactic acid may cause encephalopathy
Heinz body anemia in cats

Question 27

Clinical signs of propylene glycol

Answer 27

signs due to narcotic effects and acidosis
ataxia and CNS depression
Heinz body anemia in cats
muscle twitching in cats

Question 28

Lab diagnosis of propylene glycol

Answer 28

metabolic acidosis
hyperosmolarity
increased anion gap from lactic acid
hypoglycaemia seen
low urine SG 
Heinz body anemia in cats

Question 29

Treatment of propylene glycol

Answer 29

emesis and activated charcoal - questionable efficacy
supportive tx - IV fluids and bicarbonate therapy
metabolism inhibitors not required