Acetaminophen Toxicity in Cats

Name: Tri-County Animal Hospital
Address: 1302 Hamburg Turnpike, Wayne, NJ, 07470, US
Telephone: +19738312426

Acetaminophen Toxicity in Cats – Overview

Results from owners overdosing the cat with over-the-counter medications containing acetaminophen, a medication intended to control pain or fever in humans

Cats—genetic deficiency in a pathway that breaks down or changes (metabolizes) drugs in the liver (known as the “glucuronide conjugation pathway”); makes cats vulnerable to acetaminophen toxicity

Cats
Dogs
Most common drug toxicity in cats; considerably less frequent in dogs
Young and small dogs and cats—greater risk from owner-given single-dose acetaminophen medications

May develop 1–4 hours after dosing
Progressive depression
Rapid breathing
Darkened mucous membranes (moist tissues of body, such as gums)
Drooling (salivation)
Vomiting
Abdominal pain
Rapid breathing (known as “tachypnea”) and bluish discoloration of skin and moist tissues of body (known as “cyanosis”) due to a abnormal compound (methemoglobin) in the blood (condition known as “methemoglobinemia”) that disrupts the ability of the red blood cells to carry oxygen to the body
Fluid buildup (edema)—face, paws, and possibly forelimbs; after several hours
Chocolate-colored urine due to the presence of blood in the urine (known as “hematuria”) and the presence of methemoglobin in the urine (known as “methemoglobinuria”); especially in cats
Death

With methemoglobinemia (abnormal compound [methemoglobin] in the blood that disrupts the ability of the red blood cells to carry oxygen to the body)—must evaluate promptly; inpatient care
With dark or bloody urine or yellowish discoloration of skin and moist tissues of the body (known as “jaundice” or “icterus”)—inpatient care
Gentle handling—imperative for clinically affected pets
The veterinarian will induce vomiting (known as “emesis”) and may perform flushing of the stomach (known as “gastric lavage”)—useful within 4–6 hours of ingestion of acetaminophen
Low red blood cell count (known as “anemia”), blood in the urine (hematuria), or presence of hemoglobin in the urine (known as “hemoglobinuria”)—may require whole blood transfusion
Fluid therapy to maintain hydration and electrolyte balance
Drinking water should be available at all times

Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive
Activated charcoal—administered immediately after the animal veterinarian has induced vomiting or flushed the stomach (gastric lavage) and after vomiting is controlled; activated charcoal is used to attract and keep the remaining acetaminophen in the gastrointestinal tract
N-acetylcysteine (Mucomyst®) is administered; considered to be an antidote for acetaminophen toxicity
Other sulfur donor drugs—if N-acetylcysteine not available; sodium sulfate
1% methylene blue solution—combats methemoglobinemia without inducing red blood cell destruction (known as a “hemolytic crisis”)
Ascorbic acid—slowly reduces methemoglobinemia

Continual clinical monitoring of methemoglobinemia (abnormal compound [methemoglobin] in the blood that disrupts the ability of the red blood cells to carry oxygen to the body)
Serum liver enzyme activities to monitor liver damage
Blood glutathione level—provide evidence of the effectiveness of therapy

Never give acetaminophen to cats
Give careful attention to acetaminophen dose in dogs; acetaminophen should only be given to dogs under a veterinarian’s supervision

Liver damage and resulting scarring (fibrosis)—may compromise long-term liver function in recovered pets

Rapidly progressive methemoglobinemia (abnormal compound [methemoglobin] in the blood that disrupts the ability of the red blood cells to carry oxygen to the body)—serious sign
Methemoglobin concentrations greater than 50%—grave prognosis
Progressively rising serum liver enzymes 12–24 hours after ingestion—serious concern
Expect clinical signs to persist 12–48 hours; death owing to methemoglobinemia possible at any time
Dogs and cats receiving prompt treatment that reverses methemoglobinemia and prevents excessive liver damage may recover fully
Dogs—death as a result of liver damage may occur in a few days
Cats—death as a result of methemoglobinemia occurs 18–36 hours after ingestion