Zinc Phosphide

Question 1

Are zine phosphide rodenticides general or restricted use products?

Answer 1

Most are restricted use pesticides

Available as grain bait, past, tracking powder

Question 2

T/F: Aluminum and magnesium phosphide have similar toxic effects as zinc phosphide

Answer 2

TRUE

Question 3

How are pets exposed to zinc phosphide baits?

Answer 3

Accidental ingestion

Relay toxicosis has been observed

malicious poisoning

Question 4

What are the properties of zinc phosphide poison?

Answer 4

Grey-black powder
Garlic or dead fish odor

***when exposed to acid - liberates phosphine gas (PH3) - gas is toxic, flammable, and an irritant

relatively insoluble in water

Question 5

Acute zinc phosphide toxicosis is due to _______

Answer 5

Phosphine gas

When a patient ingests zinc phosphide - the acidic environment of the stomach/GI will liberate the toxic gas

pH below 7, and even more so pH below 4

Question 6

T/F: Ingestion of zinc phosphide is more dangerous on an empty stomach

Answer 6

FALSE

when a patient has not eaten in hours the stomach will be more alkaline, so less gas will be liberated

Question 7

What causes chronic zinc phosphide toxicosis?

Answer 7

both the zinc phosphide and phospine gas

Question 8

Toxic effects of zinc phosphide can be seen in dogs at doses of _______ mg/kg

Answer 8

20 - 40 mg/kg

Question 9

Hydrolysis and liberation of phosphine gas occurs at a pH of ____ or lower

Answer 9

4

• *hydrolysis and liberation of gas**
• vomiting or alkaline stomach pH will decrease toxicity

Question 10

Where is zinc phosphide and phosphine gas absorbed?

Answer 10

GIT

Phosphine gas can also be absorbed through inhalation

Question 11

Where is zinc phosphide and phosphine gas excreted?

Answer 11

Gas is excreted through the lungs

small amount zinc phos will be metabolized, inactivated, and excreted in the urine

Question 12

What tissues are most greatly effected by zinc phosphide toxicosis?

Answer 12

Tissue with high O2 demand: brain, heart, kidney, liver, lung

Question 13

What is the suspected MOA of phosphine gas?

Answer 13

Inhibition of oxidative phosphorylation –> decreased cellular energy production and cell death

increase in oxgen radicals resulting in peroxidation and cell damage

damage to RBCs, and blood vessels

Question 14

What clinical signs are observed in a patient with zinc phosphide toxicosis?

Answer 14

Rapid onset (min - hrs)
Anorexia, vomiting, abdominal pain, bloat-cows, increased resp rate and effort

Dogs may show CNS excitation

death within 3-48 hours due to tissue anoxia

Question 15

What lesions are associated with zine phosphide toxicosis?

Answer 15

Smell of the bait in vomitus
Gastroenteritis - may be hemorrhagic
Congestion of liver, kidney, and lungs

Question 16

What lab abnormalities are expected in a patient with zinc phosphide poisoning?

Answer 16

Metabolic acidosis, dehydration, hypocalcemia, increase serum zinc

Hypo or hyper glycemia, hyperbilirubinemia, elevated liver enzymes, azotemia, thrombocytopenia, DIC

Question 17

When sending off specimens for zinc phosphide testing, what is important about the containers used?

Answer 17

Need to be air tight. Don’t want toxic gas leaking out

samples should be frozen immediately

Question 18

T/F: Phosphine gas is a potential health hazard for owners and animal hospital staff when dealing with a patient who’s ingested zine phosphide rodenticide

Answer 18

TRUE

if you’re smelling the gas.. you’ve been exposed to a high amount (~2ppm)
*EPA safe amount = 1-0.3ppm

proper ventilation needs to take place

Question 19

What decontamination protocol is recommended for zinc phosphide poisoing?

Answer 19

Emetics - have to way risk vs benefit.. should not induce emesis with a caustic agent.. but if you don’t it will continue to be absorbed

Gastric lavage with dilute potassium

Antacids to raise gastric pH

activated charcoal - efficacy isn’t really known

Question 20

What treatment is recommended for Zinc phosphide poisoning?

Answer 20

Supportive and symptomatic

IVF, O2. CV support, Analgesics, tx Sz, GI protectants.. etc

Question 21

What is the prognosis of zinc phosphide poisoning?

Answer 21

If not signs by 8-12hr post ingestion or 12-24hrs after vomiting = good prognosis

Severe signs of tissue damage - guarded to poor

Question 22

In all symptomatic survival patients, what should be monitored after 3-5 days?

Answer 22

Monitor liver and kidney values - there can be a rare delayed injury