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Paracetamol

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026

Definition

Paracetamol (acetaminophen) is an active ingredient frequently used in human medicine with pain-relieving (analgesic) and fever-reducing (antipyretic) properties. While it is considered a relatively safe medication for humans, paracetamol poses a significant toxicity risk for dogs and especially for cats. The reason for this lies in species-specific differences in the metabolism of this active ingredient.

In dogs and cats, certain enzymes necessary for the breakdown of paracetamol are either absent or present in insufficient quantities. This leads to the accumulation of toxic metabolites in the body, which can cause severe organ damage. The liver and red blood cells are particularly affected by the toxic effect.

The peculiarity in cats lies in a pronounced deficiency of glucuronyltransferase, a key enzyme in paracetamol metabolism. This genetically determined enzyme deficiency makes cats extremely sensitive to paracetamol, so even very small doses can trigger life-threatening poisoning. While the tolerance threshold is somewhat higher in dogs, an overdose can quickly lead to severe health damage in them as well.

The most important facts at a glance

Paracetamol poisoning represents a serious and potentially life-threatening emergency for dogs and cats. Due to species-specific metabolicMetabolic refers to metabolism, i.e. the entirety of chemical processes that take place in a living organism to enable life processes. Metabolic disorders can cause a variety of Diseases in Dogs and cats. differences, even small doses of this pain reliever, commonly used in human medicine, can cause severe signs of poisoning. Cats in particular are extremely sensitive to paracetamol.

The poisoning primarily manifests through damage to red blood cells with the formation of methemoglobin, leading to oxygen deficiencyDeficiency means a lack or absence of a necessary substance required for normal bodily functions or health, such as vitamins, minerals, or hormones. in the tissues, as well as through toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. liver damage. Clinical symptoms usually develop within a few hours and include cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases., difficulty breathing, vomiting, lethargy, and in severe cases, neurological disorders leading to comaA coma is a deep state of unconsciousness where an individual cannot be awakened and does not respond to stimuli. In dogs and cats, it can be caused by severe illnesses, poisoning, or neurological problems..

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is based on the medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits., clinical symptoms, and laboratory results. TherapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. must be initiated immediately and includes decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection., the administration of the specific antidoteAn antidote is a substance used to neutralize or reverse the harmful effects of poisoning or a drug overdose. Antidotes can be specific to certain poisons or have more general detoxifying effects. N-acetylcysteine, supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. measures such as fluid therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions., and blood transfusions if necessary.

The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is favorable with early and adequate treatment; however, it worsens with an increasing time interval between ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and the start of therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions.. Careful follow-up care with regular check-ups is strongly recommended for complete recovery.

PreventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. through educating pet owners about the dangers of human medications for their pets, as well as the safe storage of medications, is the best protectionProtection refers to safeguarding against diseases or harm. In veterinary medicine, this can include protecting animals through vaccinations, the use of parasite control products, or providing a safe environment. against this preventable poisoning.

Causes, development and progression

Paracetamol has analgesicAn analgesic is a medication used to relieve Pain without affecting the patient's level of consciousness. (pain-relieving) and antipyreticAntipyretic drugs are medications used to reduce Fever. They work by acting on the heat-regulating center in the brain, thus regulating body temperature. These medications can be used in dogs and cats to reduce Fever, which is often a symptom of an infection or inflammation. (fever-reducing) effects, but it is not anti-inflammatory.
The mechanism of action for the analgesicAn analgesic is a medication used to relieve Pain without affecting the patient's level of consciousness. and antipyreticAntipyretic drugs are medications used to reduce Fever. They work by acting on the heat-regulating center in the brain, thus regulating body temperature. These medications can be used in dogs and cats to reduce Fever, which is often a symptom of an infection or inflammation. effects has not been clearly elucidated. The demonstrated inhibition of prostaglandinProstaglandins are a group of physiologically active lipid compounds found in almost all tissues and organs. They play an important role in Inflammatory conditions, pain transmission, and the regulation of blood flow and platelet function. formation in the brain is considered responsible for the effect.
The inhibitory effect of fever-inducing substances on the temperature regulation center in the brain also contributes to the observed effect of the substance.

Paracetamol poisoning in pets most often occurs due to well-intentioned but incorrect medication administration by pet owners. Owners often administer paracetamol to their animals in the belief that they can relieve Pain or Fever, without being aware of the species-specific toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity.. Self-medication based on information from the Internet or advice from acquaintances is particularly problematic.

Another common route of poisoning is the accidentalAccidental means random or unintentional and refers to events or exposures that are not deliberate, such as the accidental swallowing of foreign objects or toxins by dogs and cats. ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of paracetamol-containing medications by the animals themselves. Insecurely stored tablets or liquids can be ingested by curious animals. Combination preparations in which paracetamol is combined with other active ingredients are particularly dangerous, as these can have additional toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effects.

The minimum toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. dose in cats is approximately 10 mg/kg body weight. This means that even half of a 500 mg tablet can be life-threatening for an average cat. In dogs, the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. threshold is approximately 50-100 mg/kg body weight, although individual differences exist here as well. Young animals, older animals, and animals with pre-existing liver or kidney diseases are particularly sensitive to paracetamol.

Cumulative effects with repeated administration of smaller doses should also be considered. Regular administration of supposedly “safe” doses can also lead to signs of intoxication due to accumulation in the body.

Mechanism of action

Overdoses and Intoxication overwhelm the detoxification function of the liver and can cause the Death (necrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems.) of liver cells due to the accumulation of toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. intermediate products from the breakdown of paracetamol.
The latency periodThe latency period is the time between exposure to a disease-causing factor and the appearance of the first symptoms of the disease. At this stage, the disease is present but not yet manifest. (time between the ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of a toxinA toxin is a poison produced by living cells or organisms that can be harmful to the body upon contact or ingestion. Toxins can originate from bacteria, plants, animals, or fungi. and the appearance of the first signs of Intoxication) is only a few hours.
Paracetamol has a toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effect even in small doses for cats. Here, too, the aforementioned genetic defectA genetic defect is an abnormality or mutation in the DNA sequence of a gene that can lead to a malfunction or absence of a protein. Genetic defects can cause various genetic diseases and conditions. in cats is a primaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. concern, as it makes the usual breakdown difficult or impossible and therefore quickly leads to the accumulation of liver-damaging substances.
The same applies to young animals, whose enzyme equipment for breaking down paracetamol is still inadequate.
Furthermore, paracetamol poisoning leads to a conversion of the red blood pigment into a form unsuitable for oxygen transport (methemoglobin).

Supplements

Paracetamol is a highly toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. substance for dogs and especially cats. The toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effect is not caused by paracetamol itself, but by its metabolites, which cannot be sufficiently detoxified in either species, but especially in cats. The damage primarily affects liver cells and the erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs..

1. Pharmacokinetics of Paracetamol

AbsorptionAbsorption refers to the uptake of substances by living cells or tissues. In the context of veterinary medicine, it often refers to the absorption of nutrients, drugs, or toxins from the digestive tract into the bloodstream.: After oralOral means "through the mouth" and refers to the intake of food, medication, or other substances through the mouth. In veterinary medicine, many treatments are administered orally. administration, paracetamol is rapidly absorbed from the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract.
Metabolism: In the liver, breakdown occurs via three main pathways:
- GlucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats. (Phase II)
- Sulfation (Phase II)
- Oxidation via Cytochrome P450 (primarily CYP2E1) → Formation of the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. metabolite N-acetyl-p-benzoquinone imine (NAPQI)

The NAPQI metabolite is normally harmless when it is detoxified by glutathione (GSH). However, in the event of an overdose or a lack of glucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats., an accumulation of NAPQI occurs, which leads to massive oxidative stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being..

2. Mechanism of Action in Dogs and Cats

A) Formation of the Toxic Metabolite NAPQI

If paracetamol is ingested excessively or by species with impaired detoxification (especially cats), more paracetamol is broken down via the oxidative pathway (CYP450).
The highly reactive metabolite NAPQI is formed.
Glutathione reserves are quickly depleted → free NAPQI molecules react with cellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. components.

B) Cellular Damage Caused by NAPQI

In the liver:
- NAPQI binds to proteins in hepatocytes → cell necrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems., apoptosis, liver insufficiencyInsufficiency refers to the inadequate function or performance of an organ or system. This can include, for example, heart failure, kidney failure, or venous insufficiency.
- Particularly affected: Centrilobular hepatocytes, as they have the highest CYP activity
In erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs.:
- NAPQI oxidizes hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. to methemoglobin, which cannot transport oxygen
- Formation of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats., erythrocyte breakdown → hemolytic anemia

C) Glutathione Depletion and Systemic Oxidative Stress

Without sufficient glutathione, uncontrolled oxidative cell damage occurs
Affected organs include the liver, erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs., kidneys, and lungs

3. Species Differences

Cats: Highly Sensitive

Cats possess very little UDP-glucuronosyltransferase, which is required for the glucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats. of paracetamol.
Even small doses (10–40 mg/kg) lead to acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. methemoglobinemia and liver damage.
Even half an adultThe term "adult" refers to an individual who has reached full physical development and is considered an adult. In veterinary medicine, this term is used to describe animals that have completed growth and are of reproductive age. tablet can be fatal.
Symptoms begin within 1–6 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems..

Dogs: Moderately Sensitive

Dogs can partially detoxify paracetamol via glucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats., but poisoning can occur at doses >100 mg/kg or with repeated administration.
The main problem is hepatotoxicity; methemoglobinemia only occurs at very high doses.
Puppies and animals with pre-existing conditions are particularly at risk.

4. Clinical Consequences and Pathophysiological Changes

Target Structure	Damage by NAPQI	Consequence
Hepatocytes	Cell necrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems. due to proteinProteins are large molecules made up of amino acids and play an essential role in almost all biological processes. They are necessary for building body tissue, the function of the immune system, and as enzymes for metabolic reactions. denaturationDenaturation refers to the process in which proteins or nucleic acids lose their natural structure due to external influences such as heat, chemicals, or pH changes, often leading to a loss of function. and ROS	Liver failure, icterus, liver enzymes↑
ErythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs.	Oxidation of hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. to methemoglobin	HypoxiaHypoxia refers to a condition in which the body or a part of the body is not supplied with enough oxygen. This can lead to various symptoms, including shortness of breath, confusion, and in severe cases, organ failure., brown-colored blood, cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases.
CellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. Antioxidants	Depletion of glutathione reserves	Increased oxidative stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being.

5. Symptoms of Paracetamol Poisoning

Cats:

Early: Drooling, vomiting, apathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest., dyspneaDyspnea, also known as shortness of breath, is the subjective feeling of breathlessness or difficulty breathing. It can be a symptom of a variety of conditions, including heart disease, lung disease, and anemia., cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases. (brown mucous membranes!)
Within 6 to 12 h: Methemoglobinemia, hypothermia, facial edemaAn edema is a buildup of fluid in the body's tissues, leading to Swelling. Edema can be localized or generalized and is often a sign of an underlying condition.
Late: Hemoglobinuria, liver failure, coagulopathies, comaA coma is a deep state of unconsciousness where an individual cannot be awakened and does not respond to stimuli. In dogs and cats, it can be caused by severe illnesses, poisoning, or neurological problems., death

Dogs:

Early: ApathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest., inappetence, vomiting
12–48 h: Icterus, elevated ALT/AST, possibly methemoglobinemia
Late: Liver symptoms, coagulopathyCoagulopathy refers to a blood coagulation disorder that can lead to an increased tendency to bleed or excessive clotting. Causes can include genetic factors, diseases, certain medications, or liver dysfunction., CNSCNS stands for the central nervous system, which consists of the brain and the spinal cord. It is responsible for processing information and controls many functions of the body. disorders

6. Summary of the Toxic Mechanism

Mechanism	Consequence
Oxidation by CYP450 to NAPQI	Formation of a highly reactive metabolite
Glutathione depletion	Unprotected cell membranes, mitochondrial dysfunctionDysfunction refers to an impaired or abnormal function of an organ or system in the body. This can be due to diseases, disorders, or damage and can affect the quality of life.
Oxidation of hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs.	Methemoglobin formation, impaired oxygen transport
Damage to liver cells	NecrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems., icterus, liver failure
Formation of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats.	Erythrocyte breakdown, hemolytic anemia

Conclusion

Paracetamol poisoning in dogs and especially in cats is based on the formation of the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. metabolite NAPQI, which, if detoxification is insufficient, leads to liver cell necrosisNecrosis is the Death of tissue in a living organism, caused by factors such as injury, infection, or lack of blood supply. Necrotic tissue can cause Inflammatory conditions and further health problems., methemoglobinemia, and oxidative stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being.. Cats are particularly at risk due to their deficient glucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats. pathway. Even small amounts are considered potentially fatal. Poisoning is a veterinary emergency and requires immediate intervention.

Symptoms of intoxication

First symptoms of acute paracetamol poisoning include:

Loss of appetite
Nausea,
Vomiting
Bauchschmerzen

In cats, the minimum toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. dose for oralOral means "through the mouth" and refers to the intake of food, medication, or other substances through the mouth. In veterinary medicine, many treatments are administered orally. ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. is 10 mg/kg body weight; for dogs, it is 50 mg/kg body weight.
First symptoms appear after 1–4 hours.

The symptoms of paracetamol poisoning typically develop within 1–4 hours of ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and can vary depending on the severity and animal species. The course of poisoning can be divided into several phases:

In the early phase (1–4 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems.), the animals often show non-specific symptoms such as loss of appetite, Vomiting, drooling, and lethargy. Owners often notice a change in facial color, especially on the mucous membranes, which may have a brownish-blue discoloration (cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases.) due to the formation of methemoglobin. This is particularly visible on the gums and tongue.

In the middle phase (4–24 hours), the symptoms worsen. Affected animals suffer from shortness of breath and an increased breathing rate, as the methemoglobin formed impairs oxygen transport in the blood. Facial and paw swelling can occur, especially in cats. The animals appear increasingly weak and disoriented.

In the late phase (after 24–48 hours), the liver damage manifests with icterus / jaundiceIcterus / jaundice, also known as jaundice, is the yellowing of the skin, mucous membranes, and whites of the eyes. It is a symptom of elevated bilirubin levels in the blood, which may indicate liver disease or biliary tract problems in dogs and cats., visible on yellow-discolored mucous membranes and sclera. AbdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain, dehydrationDehydration occurs when the body loses more fluid than it takes in. This can lead to a number of problems, including headaches, Dizziness, and in extreme cases, renal failure or Cardiovascular collapse., and hypothermia can occur. In severe cases, neurological symptoms such as Seizures, clouding of consciousness up to Koma develop.

In cats, methemoglobin formation and the associated oxygen deficiencyDeficiency means a lack or absence of a necessary substance required for normal bodily functions or health, such as vitamins, minerals, or hormones. are the main focus, while in dogs, liver damage is the dominant problem. If left untreated, paracetamol poisoning can lead to Death within 2–5 days.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of paracetamol poisoning is based on the medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits., clinical examination, and specific laboratory tests. An accurate medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. is crucial, with the veterinarian inquiring about possible drug exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats.. Important information includes the amount ingested, the time of ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems., and any symptoms that have already occurred.

During the clinical examination, vital parameters are checked, and particular attention is paid to mucous membrane color, respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. rate, and neurological status. The characteristic brownish-blue discoloration of the mucous membranes is an important diagnostic indicator.

Laboratory tests are essential for diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and monitoring the course of the condition. A complete blood count can detect changes in red blood cells and the formation of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. (denatured hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs.). Determining the methemoglobin level in the blood is a specific indicator of paracetamol poisoning.

Biochemical blood tests show changes in liver enzymesEnzymes are biological catalysts that accelerate specific chemical reactions in the body without being consumed. They play a crucial role in virtually all physiological processes. (ALT, AST, ALP), which indicate liver damage. In advanced poisoning, elevated kidney values (creatinineCreatinine is a waste product that results from the breakdown of creatine, a chemical compound that provides energy in the muscles. The concentration of creatinine in the blood and urine is an important indicator of kidney function., ureaUrea, also known as carbamide, is a waste product of protein metabolism in the body. It's formed in the liver and excreted by the kidneys in urine. The urea level in the blood indicates kidney function.) and electrolyte disturbances may also occur. The acid-base balanceThe acid-base balance refers to the equilibrium between acids and bases in the body, which is important for maintaining the physiological pH in the blood and other bodily fluids. Imbalances can lead to serious health problems. provides information about a possible metabolicMetabolic refers to metabolism, i.e. the entirety of chemical processes that take place in a living organism to enable life processes. Metabolic disorders can cause a variety of Diseases in Dogs and cats. acidosisAcidosis is a condition in which the pH value in the body is too acidic, either due to an increase in acid or a loss of bases. In dogs and cats, acidosis can occur due to renal failure, diabetes, or other metabolic disorders..

Imaging techniques such as ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. can be used to assess liver and kidney morphology. In specialized laboratories, direct detection of paracetamol or its metabolites in blood or urine can be performed, but this is rarely necessary in practice, as the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually based on clinical and laboratory findings.

Therapeutic principles

If it is likely that paracetamol is still in the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract, the usual measures for decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. are indicated.
Vomiting is induced with medication, or gastric lavageLavage is a rinsing procedure that uses a liquid to clean a body cavity, organ, or wound. In veterinary medicine, lavage can be used, for example, for gastric lavage or to clean an infected wound. is performed under general anesthesia. Repeated administration of activated charcoalActivated charcoal is a fine-pored, highly adsorbing material commonly used in veterinary medicine to treat poisoning. It binds toxins in the gastrointestinal tract to prevent their absorption into the body. is always indicated.
Acetylcysteine is available as an antidoteAn antidote is a substance used to neutralize or reverse the harmful effects of poisoning or a drug overdose. Antidotes can be specific to certain poisons or have more general detoxifying effects. for dogs. It has a supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. effect with regard to the non-toxic metabolism of paracetamol.
The use of this agent in cats is controversial.
Symptomatic therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. is used to monitor and stabilize the vital functionsVital functions are essential bodily functions necessary to sustain life. These include breathing, heart rate, blood pressure, body temperature, and level of consciousness..
The focus is on the water and electrolyte balanceThe electrolyte balance refers to the balance of electrolytes in the body, which is essential for many physiological processes. Disturbances in the electrolyte balance can lead to serious health problems.. Deficits must be compensated for.
The acid-base balanceThe acid-base balance refers to the equilibrium between acids and bases in the body, which is important for maintaining the physiological pH in the blood and other bodily fluids. Imbalances can lead to serious health problems., in addition to other laboratory diagnostic findings, provides information about the oxygen transport capacity of the blood. A blood transfusion is sometimes indicated.
A complete blood count, “liver” and “kidney values” show the extent of the current Intoxication.
The therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. is supplemented by the administration of vitaminVitamins are organic compounds that are necessary in small amounts for the normal growth, development, and physiological function of the body. Vitamins must mostly be obtained through food, as the body cannot produce them or not in sufficient quantities. C.

Supplements

The treatment of paracetamol poisoning requires a rapid and comprehensive therapeutic approach. The earlier the therapy is initiated, the better the chances of success. The treatment includes several approaches:

DecontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. is the first priority, provided that ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. occurred less than 2–4 hours ago. Vomiting can be induced by administering emetics such as apomorphine in dogs or xylazine in cats. In animals with impaired consciousness or if ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. occurred longer ago, gastric lavageLavage is a rinsing procedure that uses a liquid to clean a body cavity, organ, or wound. In veterinary medicine, lavage can be used, for example, for gastric lavage or to clean an infected wound. can be performed under anesthesia. The administration of activated charcoalActivated charcoal is a fine-pored, highly adsorbing material commonly used in veterinary medicine to treat poisoning. It binds toxins in the gastrointestinal tract to prevent their absorption into the body. (1–2 g/kg body weight) every 4–6 hours over 24 hours binds paracetamol that has not yet been absorbed in the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract.

The specific antidoteAn antidote is a substance used to neutralize or reverse the harmful effects of poisoning or a drug overdose. Antidotes can be specific to certain poisons or have more general detoxifying effects. for paracetamol poisoning is N-acetylcysteine (NAC). It works by replacing glutathione, which is needed to detoxify toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. paracetamol metabolites. The dosage is 140–280 mg/kg as an initialInitial means beginning or at the start. In medicine, it can refer to the first symptoms of a disease or the first phase of a treatment process. dose, followed by 70 mg/kg every 4–6 hours over 36–48 hours. NAC can be administered oralOral means "through the mouth" and refers to the intake of food, medication, or other substances through the mouth. In veterinary medicine, many treatments are administered orally. or intravenously.

SupportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. includes infusions to stabilize the circulation and promote renal excretion of toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. metabolites. VitaminVitamins are organic compounds that are necessary in small amounts for the normal growth, development, and physiological function of the body. Vitamins must mostly be obtained through food, as the body cannot produce them or not in sufficient quantities. C (ascorbic acid) at a dose of 30 mg/kg every 6 hours can help convert methemoglobin to normal hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs.. In cats, the additional administration of acetylcysteine with vitaminVitamins are organic compounds that are necessary in small amounts for the normal growth, development, and physiological function of the body. Vitamins must mostly be obtained through food, as the body cannot produce them or not in sufficient quantities. C has proven to be particularly effective.

In severe methemoglobinemia, the administration of methylene blue (1–2 mg/kg IV) can be considered, although this should be used with caution, especially in cats. In critical cases with pronounced anemia, a blood transfusion can be life-saving.

Liver protectionProtection refers to safeguarding against diseases or harm. In veterinary medicine, this can include protecting animals through vaccinations, the use of parasite control products, or providing a safe environment. preparations such as S-adenosylmethionine (SAMe) or silymarin can be used in addition to support liver regeneration. Oxygen therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. is indicated in animals with shortness of breath and cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases..

Prognosis & follow-up care

With timely treatment of paracetamol poisoning, the prognosis is good.
Factors indicating a poor prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. are:

paracetamol ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. occurred more than 48 hours ago
blood pH is significantly lowered
kidney values (blood levels for creatinineCreatinine is a waste product that results from the breakdown of creatine, a chemical compound that provides energy in the muscles. The concentration of creatinine in the blood and urine is an important indicator of kidney function. and ureaUrea, also known as carbamide, is a waste product of protein metabolism in the body. It's formed in the liver and excreted by the kidneys in urine. The urea level in the blood indicates kidney function.) are significantly elevated
liver values in the blood are significantly elevated
hepatic comaA coma is a deep state of unconsciousness where an individual cannot be awakened and does not respond to stimuli. In dogs and cats, it can be caused by severe illnesses, poisoning, or neurological problems. with impaired brain function (disorientation, drowsiness, reduced responsiveness)
hypoglycemiaHypoglycemia is a condition in which blood sugar levels fall below the normal range. Symptoms may include tremors, sweating, Hunger, confusion, and in severe cases, loss of consciousness.
lack of plateletsPlatelets, also called thrombocytes, are cells in the blood that play a crucial role in blood coagulation. They help stop Bleeding by forming clots that seal injuries in blood vessels. (thrombocytopeniaThrombocytopenia is a condition in which the number of platelets in the blood is lower than normal, increasing the risk of mild to severe Bleeding.)
ComaA coma is a deep state of unconsciousness where an individual cannot be awakened and does not respond to stimuli. In dogs and cats, it can be caused by severe illnesses, poisoning, or neurological problems.

The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. for paracetamol poisoning largely depends on various factors: the ingested dose, the time elapsed between ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and the start of treatment, the animal species, and the animal’s individual health status before poisoning.

With early detection and adequate treatment within the first 4–6 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems., the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is generally good to guarded. Animals treated only after 24 hours or later have a significantly worse prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop., as irreversible organ damage may have already developed by then.

Factors indicating a poor prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. include pronounced methemoglobinemia (>30%), significantly elevated liver enzyme levels, coagulationCoagulation is the process of blood coagulation, in which liquid blood is transformed into a solid clot. This process is crucial for stopping Bleeding and promoting wound healing. disorders, signs of liver failure such as hypoglycemiaHypoglycemia is a condition in which blood sugar levels fall below the normal range. Symptoms may include tremors, sweating, Hunger, confusion, and in severe cases, loss of consciousness. and encephalopathy, and the presence of metabolicMetabolic refers to metabolism, i.e. the entirety of chemical processes that take place in a living organism to enable life processes. Metabolic disorders can cause a variety of Diseases in Dogs and cats. acidosisAcidosis is a condition in which the pH value in the body is too acidic, either due to an increase in acid or a loss of bases. In dogs and cats, acidosis can occur due to renal failure, diabetes, or other metabolic disorders.. Cats generally have a worse prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. than dogs due to their higher sensitivity to paracetamol.

Follow-up care after acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. poisoning is crucial for long-term recovery. Regular check-ups with blood counts and liver enzyme monitoring are required for several weeks. A liver-sparing diet with high-quality, easily digestible proteinProteins are large molecules made up of amino acids and play an essential role in almost all biological processes. They are necessary for building body tissue, the function of the immune system, and as enzymes for metabolic reactions. and reduced fat content is recommended. The administration of liver support supplements can be continued for several weeks.

Owners must be informed about possible long-term consequences such as chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. liver insufficiencyInsufficiency refers to the inadequate function or performance of an organ or system. This can include, for example, heart failure, kidney failure, or venous insufficiency.. In some cases, permanent liver damage may remain, requiring lifelong monitoring and treatment. Most animals, however, recover completely without lasting damage with adequate treatment.

Research outlook

Research in the field of paracetamol poisoning in small animals is continuously advancing. Current studies focus on several promising areas that could improve the understanding and treatment of these poisonings.

An innovative research approach focuses on improved biomarkers for the early detection of liver damage. New biomarkers such as microRNAs and specific liver enzymesEnzymes are biological catalysts that accelerate specific chemical reactions in the body without being consumed. They play a crucial role in virtually all physiological processes. could enable a more precise and earlier diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. before clinical symptoms appear. This would extend the therapeutic window and improve the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop..

Advances in antidoteAn antidote is a substance used to neutralize or reverse the harmful effects of poisoning or a drug overdose. Antidotes can be specific to certain poisons or have more general detoxifying effects. research show promising results. Modified formulations of N-acetylcysteine with improved bioavailability and longer duration of action could increase treatment efficiency. Additionally, alternative antidotes such as certain flavonoids and other antioxidants are being investigated, which could act complementarily to NAC.

In the field of liver cell regeneration, scientists are researching the use of stem cell therapies and growth factors to promote liver regeneration after toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. damage. InitialInitial means beginning or at the start. In medicine, it can refer to the first symptoms of a disease or the first phase of a treatment process. experimental studies show promising results that could potentially be translated into clinical practice in the future.

Genetic studies are dedicated to individual differences in sensitivity to paracetamol. The identification of genetic markers could help identify particularly vulnerable animals and develop individual treatment strategies.

Last but not least, researchers are working on improved preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. strategies through innovative packaging of human medicines that are inaccessible to animals, as well as educational campaigns for pet owners using digital media and apps for medication safety.

These research approaches could lead to significant improvements in the preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring., diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., and treatment of paracetamol poisoning in pets in the coming years.

Frequently asked questions (FAQs)

Why is paracetamol so dangerous for dogs and cats?

Dogs, and especially cats, do not possess the necessary enzymesEnzymes are biological catalysts that accelerate specific chemical reactions in the body without being consumed. They play a crucial role in virtually all physiological processes. to effectively metabolize paracetamol. In cats, the enzyme glucuronyltransferase is almost completely absent. This leads to the formation of toxic metabolites that can damage the liver and red blood cells, leading to life-threatening poisoning.

How much paracetamol is toxic for my pet?

For cats, as little as 10 mg/kg body weight is toxic – this corresponds to about a quarter of a 500 mg tablet for an average cat. In dogs, the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. dose is 50–100 mg/kg body weight. Individual factors such as age, health status, and genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. influence the toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. threshold.

What symptoms indicate paracetamol poisoning?

Early symptoms include Vomiting, loss of appetite, and lethargy. Characteristic signs include brownish-blue discoloration of the mucous membranes (cyanosisCyanosis refers to a bluish discoloration of the skin and mucous membranes, caused by an inadequate oxygen supply to the blood. It can be a sign of heart, lung, or blood diseases.), difficulty breathing, and facial and paw swelling. Later, jaundice, AbdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain, and neurological symptoms may occur.

How quickly do I need to act if my pet has ingested paracetamol?

Immediate action is crucial. Contact your veterinarian or a veterinary hospital immediately, ideally within the first 1–2 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems.. The sooner treatment begins, the better the chances of success.

Can I give my pet alternative medications for pain?

Only use pain medication prescribed by your veterinarian. NSAIDsNSAID (non-steroidal anti-inflammatory drug) stands for non-steroidal anti-inflammatory drugs, a class of medications used to relieve pain, reduce inflammatory conditions, and lower fever without using steroidal agents. They are a commonly used pain reliever in veterinary medicine. approved for animals, such as carprofen or meloxicam, are safe alternatives. Always consult a veterinarian before administering any medication to your pet.

How is paracetamol poisoning treated?

Treatment includes decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. (inducing Vomiting, activated charcoalActivated charcoal is a fine-pored, highly adsorbing material commonly used in veterinary medicine to treat poisoning. It binds toxins in the gastrointestinal tract to prevent their absorption into the body.), administration of the antidote N-acetylcysteine, fluid therapy, and supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. measures. In severe cases, blood transfusions and intensive care may be necessary.

Will my pet fully recover from paracetamol poisoning?

With early treatment, complete recovery is possible. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. depends on the amount ingested, the time until treatment, and the individual health status. Regular follow-up examinations are important to detect long-term consequences.

How can I prevent paracetamol poisoning in my pet?

Store all medications in locked cabinets. Never administer human medications without veterinary instruction. Inform family members and visitors about the dangers of human medications for pets.

Are there breed-specific differences in sensitivity to paracetamol?

While all cats are highly sensitive, there is evidence of breed-specific differences in dogs. Some breeds with genetic peculiarities in drug metabolism, such as Collies with the MDR1 genetic defectA genetic defect is an abnormality or mutation in the DNA sequence of a gene that can lead to a malfunction or absence of a protein. Genetic defects can cause various genetic diseases and conditions., might react more sensitively. However, scientific data on this is limited.

What should I do if I suspect my pet has accidentally ingested paracetamol but is not yet showing symptoms?

Do not wait for symptoms. Contact your veterinarian immediately and describe the situation (amount, time). Early intervention can prevent severe poisoning, even if the animal appears symptom-free.

Literature

https://www.vetpharm.uzh.ch/clinitox/toxdb/KLT_026.htm
Nelson, K. (2019). Paracetamol toxicity in dogs. The Veterinary Record, 184(19), 594.
Bates N, Rawson-Harris P, Edwards N. Common questions in veterinary toxicology. Journal of Small Animal Practice. 2022;63(4):252-263.
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Savides MC, Oehme FW, Nash SL, Leipold HW. The toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. and biotransformation of single doses of acetaminophen in dogs and cats. Toxicology and Applied Pharmacology. 2019;121(1):83-92.
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Schlesinger DP. Methemoglobinemia and anemia in a dog with acetaminophen toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity.. Canadian Veterinary Journal. 2020;36(8):515-517.
Löwe G, Löwe O. Poisonings in Dogs and Cats – A Veterinary Guide. 2nd Edition. Kreuztal: Kynos-Verlag. 2021; 208 p.