Intro to Toxicology II

Question 1

****What are the three most common routes of toxin exposure in vet medicine?

Answer 1

Oral, transdermal, respiratory, also injection!

Some toxins engage in multiple roots!

Question 2

In order for percutaneous absorption to occur…

Answer 2

The toxin must be soluble in the vehicle that is applied to the skin.
The toxin must be able to penetrate the thick keratin layer of the epidermis.
The toxin must make its way through the lower cells of the epidermis and into the vasculature.
So few toxins are absorbed through the skin, it is very difficult to get through all these layers!

Question 3

****How is percutaneous absorption enhanced?

Answer 3

Water or sweat.
Humans: pesticides on trees.
Vet med: flea preventatives; all apply to the skin, but deposited in different sites.. may be oil glands or go to the blood supply and spread systemically! More side effects if systemic!

Question 4

After a patient has ingested toxin.. the next step is..

Answer 4

DECONTAMINATION

Question 5

What is the goal of decontamination?

Answer 5

To prevent further absorption

Prevent the patient from getting worse!

Question 6

*****How do you decide the best approach for decontamination…

Answer 6

Consider the substance itself..
How toxic is it, what is the dose/dosage?
Consider the toxin its self!
How long has it been since exposed.
Species affected?
Are there any underlying diseases? (Seizures, coagulopathies..)

Question 7

What are ways to decontaminate the gastrointestinal tract targeting oral absorption?

Answer 7

Gastric evacuation... induction of emesis and gastric lavage.
Adsorbents
Cathartics (inducing diarrhea)
Whole bowel irrigation
Endoscopy

Question 8

What are the indications for inducing emesis?

Answer 8

When ingestion took place less then two hours ago.

When the ingested substance is NOT caustic.

Question 9

****What are the contraindications for inducing emesis?

Answer 9

Actively seizing..
Severely depressed/obtunded/comatose.
Species cannot vomit
When the ingested substance IS caustic!

Question 10

Inducing emesis at home in companion animals..

Answer 10

1) Hydrogen peroxide
1-2 ml/kg PO if emesis doesn't occur in 10 minutes, okay to repeat another time.
5ml = 1 teaspoon
15ml= 1 tablespoon
Syrup of Ipecac: 
Dogs 1-2 ml/kg PO
Cats: 3.3 ml/kg PO
*Can dilute with water or food!

Question 11

Inducing emesis at home “no-nos”

Do not recommend the use of…

Answer 11

TABLE SALT
Repeated administration may induce iatrogenic hypernatremia.
Recall the case study on paintball ingestion and hypernatremia can be life threatening (can affect the brain).

Question 12

****How do you induce emesis in the clinic?

DOC in the dog?

Answer 12

Apomorphine is the DOC in dogs for inducing emesis.
Can be given IV or IM or tabs can be crushed and placed in the conjunctival sac.. but need to be flushed out after use!!
Acts by stimulating the dopamine receptors in the CRTZ to induce emesis.
Not as reliable in cats and has resulted in paradoxical excitement!

Question 13

*****How do you induce emesis in the clinic for cats?

Answer 13

XYALIZINE is the DOC for emesis induction in cats.
Alpha-adrenergic agonist.
Acts by stimulating the CRTZ to induce emesis.

Question 14

Both Apomorphine and Xylazine cause what adverse effects?

Answer 14

CNS depression
Bradycardia
Respiratory depression

Question 15

*****What drug reverses apomorphine?

Answer 15

Naloxone

Question 16

****What drug reverses xylazine?

Answer 16

Yohimbine

Question 17

Gastric lavage is an alternative means of gastric evacuation..
Procedure?

Answer 17

Gastric tube is placed.
Placement is confirmed by aspiration of gastric contents.
Keep mouth lower then the chest.
Tepid water or saline (5-10 ml/kg) is introduced into the stomach, only to be withdrawn by aspiration or via gravity.
*Requires anesthesia in conscious animal.
*Requires airway protection.

Question 18

Indications of gastric lavage..

Answer 18

When induction of emesis is contraindicated.

When the ingested substance is caustic.

Question 19

The use of gastric adsorbents…

Answer 19

Insoluble material is used to bind toxins thereby decreasing their absorption by the body.
Example: Activated charcoal (AC)

Question 20

Contraindications for activated charcoal..

Answer 20

Does not bind well to strongly ionized salts like NaCl, or to small, highly polar, hydrophilic compounds like alcohols.

Question 21

Activated charcoal tip..

Answer 21

Always give the dog the option to eat it!

Question 22

Why would you use repeated doses of adsorbents?

Answer 22

Enterophepatic recycling.
Certain drugs may recirculate!
Repeated doses keeps AC in the GI tract, allowing the tract to serve as a sink for trapping toxins passing from the circulation into the intestines.

Question 23

Repeated doses of adsorbents expedites the elimination of..

Answer 23

Salicylates
Amitriptyline (human drug, Elavil, a tricyclic anti-depressant)
Carbamazepine (human drug tegretold, a mood-stabilizer)

Question 24

The use of cathartics

Definition

Answer 24

A substance used to accelerate defecation/induce diarrhea.
May be used alone or in combination with an adsorbent to further reduce absorption of toxins by decreasing time in the gut.
Maybe saline based or saccharide based.

Question 25

Example of a cathartic?

Answer 25

Activated charcoal (AC) with SORBITOL - saccharide-based.
Magnesium citrate (saline-based)
*Strongly ionized salts like NaCl
*Small, highly polar hydrophilic compounds like alcohols.

Question 26

Definition of a antidote?

Answer 26

A substance that can counteract a toxin thereby having the potential to reverse toxicosis.

Question 27

Examples of antidotes..

Answer 27

• Ethylene glycol: 4MP- also known as fomepizole.
• Acetaminophen (Tylenol): n-acetylcystine (NAC)
• Organophosphate insecticides: Pralidoxime chloride (2-PAM)

Question 28

***What species CANNOT vomit?

Answer 28

Consider that horses, rats, rodents, guinea pigs and Japanese quails cannot vomit!