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Toxicology Fall17 > Methylxanthines/Prop. glycol/Ethanol/Methanol > Flashcards

Methylxanthines/Prop. glycol/Ethanol/Methanol Flashcards

1
Q

What are some common methylxanthine alkaloids?

A

Caffeine, Theophylline (bronchodilator), and throbromine

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2
Q

In what plant does theobromine occur?

A

Cacao beans of the chocolate plant

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3
Q

What is the most common exposure or methylxanthine toxicosis we see in small animals?

A

Chocolate toxicosis

Chocolate products contain theobromine and caffeine

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4
Q

What methylxanthine alkaloid can be found in teas and asthma medication?

A

Theophylline

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5
Q

What is the absorption and metabolism of methylxanthines in dogs?

A

Readily absorbed from the GIT - widely distributed throughout the body including the CNS

Metabolized by the liver and undergoes enterohepatic recycling

excreted in the urine unchanged and as metabolites

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6
Q

What is the MOA of methylxanthine ?

A

Competitive inhibition of adenosine
Inhibition of cellular phosphodiesterase causing an increase in cAMP
Stimulation of the release of catecholamines from the adrenal medulla
Inhibition of Ca sequestration within the sarc. reticulum and increase Ca entry into cardiac and skeletal muscle

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7
Q

What is important to remember when a dog presents for ingesting chocolate?

A

Sometimes the chocolate and ball up in the stomach and that will slow down absorption - so you may have more time post ingestion to induce vomiting with a good result

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8
Q

What clinical signs will be noted in a dog with chocolate toxicity?

A

GI/Urinary tract: smooth muscle relaxation/dilation = diarrhea, vomiting, diuresis (PUPD)

Cardiac stimulation: increased rate and contractility - hypertension

CNS: cerebral stimulation and excitation - sz or tremors, hyperthermia, restlessness

***severe cases: death may occur due to cardiac arrhythmia, resp. failure, terminal sz activity

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9
Q

Theobromine specifically has the strongest effect on what organ system?

A

Cardiac stimulation

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10
Q

Caffeine stimulates the release of _______

A

catecholamines

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11
Q

Theophylline has the strongest effects on what organ systems?

A

GI and Cardiac

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12
Q

What is one lab abnormality you may see on a biochem of a dog with methylxanthine toxicosis?

A

Hypokalemia

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13
Q

What is the treatment for a dog with theobromine and caffeine toxicosis?

A

Early decontamination - induce emesis
**activated charcoal - should be repeated for up to 36-72 hours post ingestion due to enterohepatic recycling

Supportive and symptomatic care: IVF
monitor ECG - beta blockers prn- Metoprolol May note tachyarrhythmias and VPCs - lidocaine
(but some patients may have bradycardia - also should check BP before tx bradycardia - if it’s a reflex bradycardia)

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14
Q

What chemical is considered to be the “safe” anti-freeze?

A

Propylene glycol

colorless, odorless, tastes bad to animals (Unlike ethylene glycol which is sweet)

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15
Q

Propylene glycol may be used in the treatment of what condition in cows?

A

Bovine ketosis

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16
Q

T/F: Propylene glycol may be used in some semi moist foods and pharmaceuticals

A

TRUE

*diazepam

17
Q

The oral acute LD50 of propylene glycol in dogs is ___ ml/kg

A

9ml

18
Q

What is the metabolism of propylene glycol?

A

Occurs in the liver by alchohol dehydrogenase –> lactic acid–> then to pyruvic acid

those are both used in the TCA cycle - but will end up with an excess of D-lactic acid isomers –> metabolic acidosis and diuresis

19
Q

T/F: Propylene glycol undergoes lethal synthesis

A

FALSE

metabolites are not toxic

20
Q

What is the MOA of propylene glycol?

A

Osmotic diuresis, CNS depression, D-lactic adic metabolite may cause encephalopathy

21
Q

T/F: Propylene glycol will/can cause heinz body formation in cats

A

TRUE

22
Q

What is the treatment for propylene gloycol toxicosis?

A

Emetics if soon after ingestion

Supportive and symptomatic: dehydration and acidosis need to be treated

23
Q

T/F: Alcohol dehydrongenase inhibitors are recommended for the treatment of propylene glycol tox

A

False - no conversion to toxic metabolites so note necessary

24
Q

What are the sources of ethanol animals may be exposed to?

A

*alcoholic beverages
fermented bread dough
rotten fruits
inhalation and dermal use of ethanol containing shampoos

25
Q

What are the sources of methanol animals may be exposed to?

A

Ingestions of methanol containing automotive windshield fluid antifreezes or paint remover

26
Q

What are the chemical/physical properties of ethanol and methanol?

A

Volatile
Irritant
Highly lipid soluble

27
Q

What will delay the absorption of ethanol/methanol?

A

Food in the stomach

28
Q

T/F: Ethanol/Methanol are widely distributed - including the CNS

A

TRUE

29
Q

What is the metabolism of ethanol?

A

Metabolised by hepatic alcohol dehydrogenase to acetaldehyde –> then to acetate –> converted to Acetyl CoA then to CO2 and water –> excreted

30
Q

what is the MOA of ethanol and methanol?

A

CNS depression
Acetylaldehyde has vasodilatory effect and emetic effect

  • ethanol inhibits ADH –> diuresis/dehydration (PUPD)
  • irritation to MM
31
Q

What does chronic ethanol/methanol toxicosis cause?

A

Liver and kidney damage - this is uncommon

32
Q

What PM lesions may be noted in an animal that died of ethanol/methanol poisoning?

A

Congestion of GI mucosa

Congestion of liver, kidney, lunges

33
Q

What is the treatment for ethanol toxicosis?

A

No specific antidote

Emetics if ingestion is recent; activated charcoal is not very effective

Supportive and symptomatic

34
Q

What treatment options are there for methanol toxicosis?

A

Ethanol and fomepizole can be used as antidotes of methanol toxicosis

35
Q

What can be used to antagonize the CNS depression causes by ethanol/methanol toxicosis?

A

Naloxone

Toxicology Fall17 (38 decks)

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