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Lidocaine

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

Definition

Lidocaine is a local anesthetic from the amide group and is widely used in both human and veterinary medicine. It is primarily used for local pain control in minor procedures, as an antiarrhythmic for cardiac arrhythmia, and as ointments and gels for topical anesthesia. The active ingredient blocks voltage-gated sodium channels in cell membranes, inhibiting the conduction of nerve impulses. This property makes lidocaine an effective pain reliever, but overdose or improper use poses significant risks for small animals.

Lidocaine toxicity differs significantly between animal species. Cats are particularly sensitive due to their limited capacity for glucuronidation—an important metabolic pathway for breaking down medications in the liver. While dogs have somewhat higher tolerance, even small overdoses can cause severe signs of poisoning in them as well. The therapeutic window—the gap between an effective and a toxic dose—is relatively narrow in both species.

The most important facts at a glance

Lidocaine poisoning is a relevant toxicological problem in small animal medicine and can result from both medical use and 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. 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.. The active ingredient blocks sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels, thereby impairing impulse conduction in nerve and heart muscle cells. Cats in particular are at risk due to their limited metabolism.

Clinical signs primarily affect the nervous system with symptoms such as restlessness, tremor and convulsions, and the cardiovascular system in the form of arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. and blood pressure changes. 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 mainly 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. and the characteristic symptom pattern, supported by electrocardiogramSee ECG. examinations.

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 decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. measures, symptomatic treatment of neurological and cardiovascular symptoms, 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. Intravenous lipid 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. has proven to be a promising treatment option in severe intoxication / poisoningIntoxication / poisoning refers to poisoning caused by the intake of toxic substances. This can be caused by medications, drugs, chemicals, or other poisons and often requires medical treatment..

With early recognition and appropriate treatment, 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, although recovery time in cats may be longer due to their delayed metabolism. Follow-up care focuses on monitoring possible long-term effects and preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of renewed 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..

For veterinarians and pet owners, it is important to know the risks of lidocaine and to take species-specific differences into account when using it. Careful dosing and safe storage of lidocaine-containing products are crucial to prevent poisoning cases.

Causes, development and progression

Lidocaine increases the excitation threshold in nerve cells and slows impulse conduction.
In the heart muscle, lidocaine reduces excitability, the speed of impulse conduction and contractile force, thereby lowering the risk of arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems..

Lidocaine poisoning in pets mainly arises from three scenarios: iatrogenicIatrogenic refers to conditions or diseases that arise as a direct result of medical treatments or interventions. Examples of iatrogenic problems in dogs and cats can include medication side effects or post-operative complications. overdose during veterinary treatment, 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. 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. of lidocaine-containing products, or improper use by pet owners.

In iatrogenicIatrogenic refers to conditions or diseases that arise as a direct result of medical treatments or interventions. Examples of iatrogenic problems in dogs and cats can include medication side effects or post-operative complications. poisoning, excessively high doses, overly rapid intravenous administration, or unintended intravascular injection during what was meant to be subcutaneousSubcutaneous means "under the skin." In medicine, it refers to the administration of drugs or the placement of implants directly under the skin. use can lead to 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. plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels. Animals with impaired liver or kidney function are particularly at risk, as metabolism and excretion of the active ingredient may be delayed.

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. 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. usually occurs when animals gain access to the owner’s medications. Although orally ingested lidocaine is subject to a significant first-pass effect in the liver, 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. plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels can still occur if larger amounts are ingested. In cats, this effect is even more pronounced due to their 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. characteristics.

Another common cause is improper use by pet owners who apply human lidocaine products to their pets. The concentration of these products is often unsuitable for animals, and the dose is frequently calculated incorrectly. Combination products are particularly dangerous because, in addition to lidocaine, they may contain other active ingredients that can be 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. to animals.

Mechanism of action

Lidocaine is absorbed 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. 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.. It is also dangerous because cats have limited ability to break it down.
The toxic effects of lidocaine initially affect the central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior. (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.). The 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. is more sensitive and reacts at lower lidocaine plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels than, for example, the cardiovascular system.
However, for the potentially fatal outcome of lidocaine intoxication / poisoningIntoxication / poisoning refers to poisoning caused by the intake of toxic substances. This can be caused by medications, drugs, chemicals, or other poisons and often requires medical treatment., the effects on the cardiovascular system are more important.
Slowed impulse conduction in the heart, up to conduction blocks, leads to pronounced cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. and ultimately cardiac arrest.
In cats, a genetically limited ability to metabolize it in the liver leads to persistently high plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels during intoxication / poisoningIntoxication / poisoning refers to poisoning caused by the intake of toxic substances. This can be caused by medications, drugs, chemicals, or other poisons and often requires medical treatment..

Supplements

ToxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. mainly affects the 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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.) and the cardiovascular system.

1. Principle of Lidocaine Action (Physiological and Toxicological)

Lidocaine selectively blocks voltage-gated sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels (Na⁺ channels) in neuronal and cardiac cell membranes. This inhibits the conduction of action potentials in nerves and heart muscle cells.

A) in the Therapeutic Range:

Inhibition of Na⁺ channels leads to reversible interruption of nerve conduction → local pain relief.
In the heart: Shortening of action potential duration → treatment of ventricular tachyarrhythmias.

b) In the toxic range:

Lidocaine also inhibits central and cardiac sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels.
This causes excessive inhibition of neuronal excitation conduction and cardiac impulse conduction, leading to severe neurological and cardiovascular symptoms.

2. Pathophysiology of lidocaine poisoning

Central nervous system – first target of toxicity

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. phase: Reversible blockade of inhibitory interneurons → excess excitation, e.g., restlessness, muscle tremors, ataxia.
Advanced phase: GeneralizedGeneralized means that a disease or condition affects a large part of the body or multiple organ systems. Generalized diseases can show systemic symptoms and may require more comprehensive treatment. Na⁺ channel blockade → depressionDepression refers to a state of reduced mood and activity. In dogs and cats, it can be triggered by various factors, including illness, trauma, or changes in the environment. of overall neuronal activity → lethargy, seizures, 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..

Cardiovascular System

Blockade of cardiac Na⁺ channels → delayed impulse conduction, prolonged depolarization.
Result: bradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease., AV block, hypotension, ventricular arrhythmias, and in extreme cases ventricular fibrillationFibrillation is an irregular, often rapid heart rate that leads to a chaotic rhythm in the atria or ventricles of the heart. This can impair cardiac output and often requires medical treatment. or cardiac arrest.
Myocardial contractility can also be depressed by lidocaine → risk of cardiogenic shock.

Further Effects

Vasodilation due to influence on smooth vascular musculature → blood pressure drop.
At high doses: 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., respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. depressionDepression refers to a state of reduced mood and activity. In dogs and cats, it can be triggered by various factors, including illness, trauma, or changes in the environment.

3. Species Differences and Risk Factors

Dog:

Generally better tolerated than cats.
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 i.v.: approximately >20 mg/kg.
Symptoms often appear rapidly after intravenous or intravascular administration.

Cat:

Very sensitive to lidocaine because hepatic metabolism (especially 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.) is limited.
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 i.v.: as low as 6–10 mg/kg.
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. use is particularly dangerous (e.g., in the mouth): leads to severe 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, hypersalivation, collapse.

4. Clinical Symptoms of Lidocaine Poisoning

Organ System	Symptoms
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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.)	Restlessness, muscle tremors, ataxia, seizures, 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.
Cardiovascular	BradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease., hypotension, arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems., AV block, cardiac arrest
Respiration	Shortness of breath, hypoventilation, 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.
General	Weakness, hypersalivation, hyperthermiaHyperthermia refers to an elevated body temperature beyond the normal range. In dogs and cats, this can be caused by overheating, Fever, or certain diseases, and often requires urgent medical attention. due to muscle activity

5. Mechanistic Summary

Target Structure	Mechanism	Consequence
Voltage-gated Na⁺ channels	Blockade of fast sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels	Inhibition of impulse conduction in nerves and myocardiumThe myocardium is the heart muscle itself, responsible for the heart's contraction, which enables blood circulation in the body. Diseases of the myocardium can impair the heart's pumping function.
Interneurons in the 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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.)	Disinhibition due to early blockade → later total inhibition	Seizures, 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. depressionDepression refers to a state of reduced mood and activity. In dogs and cats, it can be triggered by various factors, including illness, trauma, or changes in the environment., respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. arrest
Heart muscle	Delayed spread of excitation → reduced contraction	BradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease., hypotension, arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems.
Smooth vascular musculature	Vasodilation	Blood pressure drop, circulatory failure

6. Conclusion

Lidocaine poisoning in dogs and cats results from systemic overdose and mainly affects the 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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.) and the cardiovascular system. The underlying mechanism is the blockade of voltage-gated sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels, which massively disrupts the electrical excitability of nerve cells and cardiomyocytes. While dogs show moderate tolerance, cats are extremely sensitive, especially with 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 intravenous 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.. Lidocaine poisoning is a veterinary emergency and requires immediate symptomatic treatment, especially in cases of convulsions or circulatory weakness.

Symptoms of intoxication

Regarding the nervous system

Confusion
Restlessness
Tremors and
Convulsions (tonic-clonic)

Regarding the cardiovascular system

Initially increased heart rate and blood pressure
Later decrease in heart rate and blood pressure
Cardiac arrhythmias
Ventricular fibrillationFibrillation is an irregular, often rapid heart rate that leads to a chaotic rhythm in the atria or ventricles of the heart. This can impair cardiac output and often requires medical treatment.
Cardiac arrest (asystole)
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.
RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. Arrest

The clinical signs of lidocaine poisoning primarily affect the nervous system and the cardiovascular system, with neurological symptoms usually appearing first. Symptoms usually develop rapidly after 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. and can vary in severity depending on the degree of intoxication / poisoningIntoxication / poisoning refers to poisoning caused by the intake of toxic substances. This can be caused by medications, drugs, chemicals, or other poisons and often requires medical treatment..

In the 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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.), affected animals initially show restlessness, disorientation and confusion. As plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels rise, muscle tremors (tremor), ataxia and coordination disorders may occur. In severe cases, tonic-clonic convulsions develop, which can progress 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.. These neurological symptoms result from blockade of inhibitory neurons in the 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. (central nervous systemThe CNS (central nervous system) consists of the brain and spinal cord. It is responsible for processing information and controls most functions of the body and behavior.), leading to overactivity of excitatory systems.

Cardiovascular effects typically begin with 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. tachycardiaTachycardia refers to an unusually fast heartbeat with a resting heart rate of over 100 beats per minute. It can indicate physical exertion, stress, illness, or heart problems. and hypertensionHypertension, or high blood pressure, is a condition in which the blood pressure in the arteries is consistently elevated. In dogs and cats, this can lead to damage to organs such as the heart, kidneys, and eyes, and requires medical treatment., followed by progressiveProgressive describes a condition or disease that worsens over time. This term is often used to characterize the course of an illness that causes increasingly severe symptoms or damage. bradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease. and hypotension with ongoing 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.. By blocking sodiumSodium is a vital electrolyte that plays a key role in regulating water balance, blood pressure, and nerve and muscle activity. Unbalanced sodium levels can lead to various health problems in dogs and cats. channels in the heart muscle, disturbances in impulse conduction occur, which can manifest as various arrhythmias. In severe cases, ventricular fibrillationFibrillation is an irregular, often rapid heart rate that leads to a chaotic rhythm in the atria or ventricles of the heart. This can impair cardiac output and often requires medical treatment. and ultimately cardiac arrest can occur. These cardiovascular effects are particularly dangerous because they can persist even after the neurological symptoms have subsided.

In cats, symptoms may last longer and be more severe due to delayed breakdown of lidocaine. In addition, 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. symptoms such as vomiting and drooling may occur, especially 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. 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 the active ingredient.

Diagnosis

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 lidocaine poisoning is based primarily 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 signs, and ruling out other causes. A thorough discussion with the owner is crucial to obtain information about possible sources of 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., timing of 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., and the estimated amount ingested.

The clinical exam includes a full neurological evaluation and cardiovascular assessment. Particular attention is paid to heart rate, heart rhythm, and blood pressure. An electrocardiogramSee ECG. is an important diagnostic tool because lidocaine can cause characteristic changes, including sinus bradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease., prolonged PR intervals, widened QRS complexes, and various forms of heart block.

Laboratory tests mainly serve to rule out other causes and assess organ function. A complete blood count, serum electrolytesElectrolytes are minerals in the body that carry an electric charge and perform vital functions such as regulating fluid balance, acid-base balance, and nerve and muscle activity. The main electrolytes include sodium, potassium, chloride, and magnesium., kidney values and liver values should be measured to assess the patient’s overall condition and detect possible complications. Direct measurement of lidocaine plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels is rarely available in veterinary practice and is often not timely enough for 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. treatment.

Differential diagnoses include other poisonings (especially from other local anesthetics, antiarrhythmics, or CNS-active substances), 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. disorders, primaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. neurological diseases, and primaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. cardiac arrhythmias. The temporal correlation between 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. and onset of symptoms, the characteristic pattern of clinical signs, and the response to 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. support 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..

Therapeutic principles

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. 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 lidocaine, decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. by inducing vomiting, administering 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. and/or intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. lavage depends on the time that has passed between ingestion of lidocaine and presentation to the veterinarian.
There is no 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..
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 symptomatic.
In the event of cardiac arrest, immediate resuscitationResuscitation includes measures to revive animals after a cardiac arrest or severe respiratory depression. These may include chest compressions and artificial respiration. is required.
Because cats break down lidocaine more slowly, cardiovascular monitoring needs to be extended and repeated resuscitationResuscitation includes measures to revive animals after a cardiac arrest or severe respiratory depression. These may include chest compressions and artificial respiration. may be necessary.
In human medicine, intravenous lipids are administered immediately after successful resuscitationResuscitation includes measures to revive animals after a cardiac arrest or severe respiratory depression. These may include chest compressions and artificial respiration..
The effect of a lipid infusion is explained by the binding of fat-soluble lidocaine molecules to the infused lipids.
Seizures and tremor are controlled with medication so that symptoms are relieved as much as possible, but deep anesthesiaAnesthesia refers to the state of insensitivity to pain and can be partial (local anesthesia) or for the entire body (general anesthesia). It is used to keep patients pain-free during surgical procedures. is not the goal. By repeatedly giving smaller individual doses and combining several medications, the dose of anticonvulsantsAnticonvulsants, also called antiepileptic drugs, are medications used to control or prevent seizures. They are used in dogs and cats with epilepsy or other conditions that cause seizures. can be reduced and the risk of side effects minimized.

Supplements

Treating lidocaine poisoning requires a fast, structured approach. Since there is no 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., 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 based on three pillars: decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection., symptomatic treatment, 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.

If oral 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. was recent, decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. can be performed by inducing vomiting (only in an alert animal and within the first 1–2 hours) and administering 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. (1–4 g/kg body weight). With dermal 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., the affected area should be thoroughly rinsed with lukewarm water to remove any remaining lidocaine.

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 guided by the predominant clinical signs. For convulsions, anticonvulsantsAnticonvulsants, also called antiepileptic drugs, are medications used to control or prevent seizures. They are used in dogs and cats with epilepsy or other conditions that cause seizures. such as diazepam (0.5–2 mg/kg IV) or phenobarbital (2–6 mg/kg IV) are used. It is important to titrate the dose to avoid excessive respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. depressionDepression refers to a state of reduced mood and activity. In dogs and cats, it can be triggered by various factors, including illness, trauma, or changes in the environment.. For cardiovascular complications, specific antiarrhythmics may be indicated depending on the type of arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems.. For bradycardiaBradycardia refers to a slower than normal heart rate, typically below 60 beats per minute in adults. It can occur in healthy individuals, especially athletes, but can also be an indication of heart disease., atropine (0.02–0.04 mg/kg IV) can be administered, while hypotension is treated with 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, if needed, vasopressors.

A promising 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. option for severe lidocaine poisoning is intravenous lipid infusion (Lipid Rescue 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.). This treatment is based on the principle that lipophilic substances such as lidocaine can be bound in a lipid emulsion, reducing their plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. concentration and thus their 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. The protocol typically includes 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. bolus of 20% lipid emulsion (1.5 ml/kg over 1–2 minutes), followed by a continuous infusion (0.25 ml/kg/min for 30–60 minutes).

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 include 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. to promote renal eliminationElimination refers to the process by which waste products and toxins are removed from the body. This includes excretion via the kidneys (urine), intestines (stool), lungs (breath), and skin., oxygen supplementationSupplementation is the addition of nutrients, vitamins, or other substances to a normal diet to compensate for deficiencies or to support general health and well-being. In dogs and cats, supplementation may vary depending on their health condition and nutritional needs. in 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., and in severe cases possibly mechanical ventilation. Continuous monitoring of vital signs, especially heart function, is essential in order to respond quickly to changes.

Prognosis & follow-up care

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 good.

With mild to moderate poisoning, complete recovery without long-term effects is usually expected after successful treatment. Neurological symptoms usually resolve within 24 hours, while cardiovascular effects may persist somewhat longer. In cats, the recovery phase may be prolonged due to their delayed metabolism.

Severe intoxication / poisoningIntoxication / poisoning refers to poisoning caused by the intake of toxic substances. This can be caused by medications, drugs, chemicals, or other poisons and often requires medical treatment. with prolonged convulsions or serious cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. can potentially lead to permanent neurological damage or myocardial impairment. In such cases, close follow-up with regular cardiologyCardiology is the branch of medicine that deals with diseases and disorders of the heart and circulatory system. Cardiologists diagnose and treat heart conditions such as coronary artery disease, heart failure, and arrhythmias. and neurological check-ups is indicated.

Follow-up initially includes inpatient monitoring for at least 24–48 hours after the acute symptoms have subsided, especially in cats. After discharge, owners should watch for possible relapses or delayed-onset symptoms. These include subtle neurological abnormalities such as changes in behavior, coordination disorders or weakness, as well as signs of heart problems such as reduced performance, cough or shortness of breath.

Preventive measures to avoid re-exposureRe-exposure refers to renewed Contact with an allergen, toxin, or pathogen after previous exposure. In dogs and cats, this can lead to a renewed or intensified reaction, especially in cases of allergies or sensitivities. are an essential part of follow-up care. These include safely storing medications out of pets’ reach and educating owners about the risks of self-medicating their animals with human products.

Research outlook

Research into lidocaine toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. in small animals is continuously evolving, with several promising approaches being pursued. One focus is on optimizing Lipid Rescue 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., which has been increasingly adopted in veterinary practice in recent years. Current studies are investigating the optimal dosage, administration rate, and composition of lipid emulsions for different animal species and degrees of poisoning.

Another area of research involves developing specific biomarkers for early detection of local anesthetic-induced toxicities. These could help identify at-risk patients early and initiate preventive measures. In parallel, new lidocaine formulations with improved pharmacokinetic properties and lower toxicity potential are being researched, tailored specifically to the needs of different animal species.

Special attention is also being paid to genetic factors that influence individual sensitivity to lidocaine. By identifying genetic polymorphisms associated with an increased risk of poisoning, personalized dosing regimens could be developed in the future to minimize toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. risk.

Integrating point-of-care tests for rapid measurement of lidocaine plasmaPlasma is the liquid part of blood in which blood cells are suspended. It contains water, salts, proteins, and other substances and serves as a transport medium for nutrients, hormones, and waste products. levels in veterinary practice could improve diagnostic certainty and enable more targeted 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.. Such rapid tests are currently in development and may become available in the coming years.

Last but not least, research is also focusing on the long-term prognosis after surviving lidocaine poisoning. Longitudinal studies are examining possible subtle neurological or cardiac sequelae and their impact on the affected animals’ quality of life.

Frequently asked questions (FAQs)

How quickly do the symptoms of lidocaine poisoning appear?

Symptoms of lidocaine poisoning can occur very quickly. With intravenous administration, the first signs are often seen within minutes, while with 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. it typically takes 30–60 minutes. In cats, symptoms can last longer due to delayed breakdown.

Can I apply human lidocaine ointment to my pet for minor injuries?

No, using human lidocaine products on pets without veterinary instructions is not recommended. The concentration is often unsuitable for animals, and there is a risk of overdose from 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. through licking. Always consult a veterinarian about suitable treatment options.

Which animals are particularly sensitive to lidocaine?

Cats are particularly sensitive to lidocaine due to their limited metabolism. Small dog breeds, young animals, and animals with liver or kidney disease also have an increased risk of poisoning.

How is lidocaine 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. measures (if possible), symptomatic therapy for neurological and cardiovascular symptoms, intravenous 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 in severe cases intravenous lipid 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.. Inpatient monitoring is usually necessary.

Is there 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 lidocaine poisoning?

There is no 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 lidocaine. Treatment aims to control symptoms and support the body in eliminationElimination refers to the process by which waste products and toxins are removed from the body. This includes excretion via the kidneys (urine), intestines (stool), lungs (breath), and skin. of the active ingredient. Intravenous lipid 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. can help bind lidocaine in the bloodstream and reduce its toxic effects.

Can my pet fully recover after lidocaine poisoning?

With early recognition and appropriate treatment, 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 a full recovery is good. However, severe poisoning with prolonged convulsions or cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. can lead to permanent damage.

How can I prevent lidocaine poisoning in my pet?

Store all medications securely out of pets’ reach. Use lidocaine products only as directed by a veterinarian and at the prescribed dose. Make sure your pet cannot lick treated skin areas.

What alternative pain relievers are safer for pets than lidocaine?

For pain management in pets, there are various veterinary-approved medications available, including non-steroidalNon-steroidal refers to medications or substances that are not steroids and often have anti-inflammatory, analgesic, or antipyretic effects. They are used in dogs and cats to treat Pain and Inflammatory conditions. anti-inflammatory drugsAnti-inflammatory drugs are medications that reduce inflammation. They can be divided into nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids and are used in dogs and cats to reduce Inflammatory conditions and Pain. (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.) such as meloxicam or carprofen, as well as opioids. The choice of a suitable pain reliever should always be made in consultation with the veterinarian.

How long does it take for lidocaine to be metabolized by my pet’s body?

The eliminationElimination refers to the process by which waste products and toxins are removed from the body. This includes excretion via the kidneys (urine), intestines (stool), lungs (breath), and skin. half-life of lidocaine is about 1–2 hours in dogs; in cats it can be significantly longer due to limited metabolism (up to 4–6 hours). Complete eliminationElimination refers to the process by which waste products and toxins are removed from the body. This includes excretion via the kidneys (urine), intestines (stool), lungs (breath), and skin. usually takes about 4 to 5 times the half-life.

Can lidocaine poisoning be fatal?

Yes, untreated severe lidocaine poisoning can lead to death due to cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems., respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. paralysisParalysis is the complete loss of muscle activity in one or more areas of the body, which can lead to immobility and loss of sensation. Paralysis can be caused by injuries, illnesses, or disorders of the nervous system. or convulsions. With early recognition and appropriate treatment, however, the risk is significantly reduced.

Literature

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