Lidocaine
Lidocaine is a local anesthetic from the amide group, widely used in both human and veterinary medicine. It is primarily used for local pain relief during minor procedures, as an antiarrhythmic for cardiac arrhythmias, and in the form of ointments and gels for topical anesthesia. The active substance blocks voltage-gated sodium channels in cell membranes, thereby inhibiting the transmission of nerve impulses. This property makes lidocaine an effective pain reliever, but it carries significant risks for small animals if overdosed or used incorrectly.
The toxicity of lidocaine differs significantly between various animal species. Cats are particularly sensitive due to their limited ability to glucuronidate – an important metabolic pathway for drug breakdown in the liver. While dogs show a slightly higher tolerance, even small overdoses can lead to severe signs of poisoning in them. The therapeutic window, i.e., the margin between effective and toxic doses, is relatively narrow in both animal species.
The most important facts at a glance
Lidocaine poisonings represent a relevant toxicological problem in small animal medicine, which can arise from both medical application 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 substance 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 cardiac muscle cells. Cats are particularly at risk due to their limited metabolism.
Clinical signs primarily manifest in the nervous system with symptoms such as restlessness, tremors, and seizures, as well as in the cardiovascular system in the form of arrhythmias 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 mainly 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. and the characteristic symptom pattern, supported by 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 emulsion 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 for severe intoxications.
With early detection and adequate 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 the recovery time in cats can be longer due to their delayed metabolism. Follow-up care focuses on monitoring for possible long-term consequences and preventing 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..
It is important for veterinarians and pet owners to be aware of the risks of lidocaine and to consider species-specific characteristics during its use. Careful dosing and safe storage of lidocaine-containing preparations are crucial to prevent poisoning cases.
Causes, development and progression
Lidocaine increases the excitation threshold in nerve cells and slows down impulse conduction.
In the heart muscle, lidocaine reduces excitability, the speed of impulse conduction, and contractile force, thereby reducing the risk of arrhythmias.
Lidocaine poisoning in pets primarily 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 treatments, 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 preparations, or improper application by pet owners.
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 occurs when 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 result from excessive dosing, overly rapid intravenous administration, or unintentional intravascular injection during what should be subcutaneousSubcutaneous means "under the skin." In medicine, it refers to the administration of drugs or the placement of implants directly under the skin. application. Animals with impaired liver or kidney function are particularly at risk, as the metabolism and excretion of the active substance 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 access their owner’s medications. Although lidocaine undergoes a significant first-pass effect in the liver when taken orally, 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 large quantities are ingested. This effect is even more pronounced in cats 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. peculiarities.
Another common cause is improper application by pet owners who use human lidocaine preparations on their pets. The concentration of these preparations is often unsuitable for animals, and the dosage is frequently miscalculated. Combination preparations containing other active ingredients besides lidocaine, which 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, are particularly dangerous.
Mechanism of action
Lidocaine is absorbed when taken orally. It is also dangerous in cats due to their limited ability to break it down.
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 of lidocaine primarily affects 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.. This system is more sensitive and reacts at a lower 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. lidocaine level than, for example, the cardiovascular system.
However, the effects on the cardiovascular system are more significant for the potential fatal outcome of lidocaine intoxications.
The slowing of impulse conduction in the heart, leading to blockages, results in pronounced cardiac arrhythmias and ultimately cardiac arrest.
In cats, the genetically determined limited breakdown capability in the liver leads to a prolonged 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. level during intoxications.
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. primarily affects 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.) 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 leads to excessive inhibition of neuronal excitation conduction and cardiac impulse conduction, resulting in severe neurological and cardiovascular symptoms.
2. Pathophysiology of Lidocaine Poisoning
Central Nervous System – First Target Structure 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 → excitation excess, 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.
- Consequence: 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, 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 be additionally depressed by lidocaine → risk of cardiogenic shock.
Further Effects
- Vasodilation due to influence on smooth vascular musculature → blood pressure drop.
- In 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 due to impaired 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.).
- 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. administration (e.g., in the 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. cavity) is particularly dangerous: leads to intense 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. disturbances, 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. | 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, arrhythmias, AV block, cardiac arrest |
| Respiration | 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., 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. | 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 impulse propagation → reduced contractility | 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, arrhythmias |
| Smooth vascular musculature | Vasodilation | Blood pressure drop, circulatory failure |
6. Conclusion
Lidocaine poisoning in dogs and cats results from systemic overdose and primarily 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. and 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 severely disrupts the electrical excitability of nerve cells and cardiomyocytes. While dogs show moderate tolerance, cats are extremely sensitive, especially to 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 for seizures or circulatory weakness.
Symptoms of intoxication
Regarding the nervous system
- Confusion
- Restlessness
- Tremors and
- Seizures (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 manifest in the nervous system and cardiovascular system, with neurological symptoms generally appearing first. The 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.
In 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., affected animals initially show restlessness, disorientation, and confusion. With increasing 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, muscle tremors, ataxia, and coordination disorders may occur. In severe cases, tonic-clonic seizures can develop, which may progress to a 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 arise from the 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., leading to an 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 continued 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 blockade of 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 leads to disturbances in impulse conduction, 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 as they can persist even after neurological symptoms subside.
In cats, symptoms may persist longer and be more severe due to the delayed metabolism of lidocaine. Additionally, 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 salivation may occur, 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. 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 substance.
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 lidocaine poisoning is primarily 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 the exclusion of other causes. A thorough questioning of the owner is crucial to obtain information about possible 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. sources, time 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 estimated ingested amount.
The clinical examination includes a complete neurological evaluation and cardiovascular assessment. Special attention is paid to heart rate, heart rhythm, and blood pressure. An electrocardiogramSee ECG. (ECG) is an important diagnostic tool, as 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 diagnostic tests primarily serve to exclude other causes and assess organ function. A complete blood count, serum electrolytes, kidney and liver values should be determined to assess the patient’s general condition and identify possible complications. Direct determination 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 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.
Differentially, other poisonings (especially by 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 must be excluded. 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 symptom onset, 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
In cases of 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. lidocaine 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., 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 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. depends on the time elapsed between lidocaine intake 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 case 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 necessary.
Due to the delayed metabolism of lidocaine in cats, cardiovascular function monitoring should 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 lipid administration is given 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 tremors are controlled with medication to alleviate symptoms 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 administering 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
The treatment of lidocaine poisoning requires a rapid and structured approach. Since 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. exists, 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.
In cases of recent 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., 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 achieved by inducing vomiting (only in conscious animals 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 BW). For 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 directed at the predominant clinical signs. For seizures, 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 i.v.) or phenobarbital (2–6 mg/kg i.v.) 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 i.v.) 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 necessary, vasopressors.
A promising therapeutic option for severe lidocaine poisoning is intravenous lipid emulsion 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 like lidocaine can be bound in a lipid emulsion, thereby 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. for 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 parameters, especially cardiac function, is essential to react quickly to changes.
Prognosis & follow-up care
The prognosis is good.
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 lidocaine poisoning is generally favorable with early detection and adequate treatment. The course and chances of recovery largely depend on the amount ingested, the time until 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. begins, and the individual health status of the animal.
In cases of mild to moderate poisoning, complete recovery without long-term consequences is generally expected after successful treatment. Neurological symptoms usually resolve within 24 hours, while cardiovascular effects may persist slightly longer. In cats, the recovery phase may be prolonged due to their delayed metabolism.
Severe intoxications with prolonged seizures or severe cardiac arrhythmias can potentially lead to permanent neurological damage or myocardial impairment. In such cases, close follow-up with regular cardiological and neurological examinations is indicated.
Follow-up care initially includes inpatient monitoring for at least 24–48 hours after the 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. symptoms subside, especially in cats. After discharge, owners should watch for possible relapses or delayed symptoms. These include subtle neurological abnormalities such as altered behavior, coordination disorders, or weakness, as well as signs of heart problems such as exercise intolerance, coughing, or 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..
Preventive measures to avoid 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. are an essential part of follow-up care. These include safely storing medications out of reach of pets and educating owners about the risks of self-medicating their animals with human medical preparations.
Research outlook
Research in the field of lidocaine toxicity in small animals continues to evolve, with several promising approaches being pursued. One focus is on optimizing lipid emulsion rescue therapy, which has increasingly found its way into veterinary practice in recent years. Current studies are investigating the optimal dosage, administration rate, and composition of lipid emulsions for various animal species and degrees of poisoning.
Another area of research concerns the development of specific biomarkers for the early detection of local anesthetic-induced toxicities. These could help identify at-risk patients early and initiate preventive measures. In parallel, new formulations of lidocaine with improved pharmacokinetic properties and lower toxicity potential are being researched, specifically tailored 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.
The integration of point-of-care testing methods for rapid determination of lidocaine plasma levels in veterinary practice could increase diagnostic certainty and enable more targeted therapy. Such rapid tests are currently under development and could become available in the coming years.
Last but not least, research also addresses the long-term 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. after recovery from lidocaine poisoning. Longitudinal studies are investigating possible subtle neurological or cardiac sequelae and their impact on the quality of life of affected animals.
Frequently asked questions (FAQs)
- How quickly do the symptoms of lidocaine poisoning appear?
Symptoms of lidocaine poisoning can appear very quickly. With intravenous administration, initial signs are often observed within minutes, while with 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., it typically takes 30–60 minutes. In cats, symptoms may persist longer due to delayed metabolism.
- Can I apply human lidocaine ointment to my pet for minor injuries?
No, the use of human lidocaine preparations on pets without veterinary instruction 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. during licking. Always consult a veterinarian for appropriate 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 diseases 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 help the body eliminate the active substance. 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 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.
- Can my pet fully recover after lidocaine poisoning?
With early detection and adequate 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 full recovery is good. However, severe poisoning with prolonged seizures or cardiac arrhythmias can lead to permanent damage.
- How can I prevent lidocaine poisoning in my pet?
Store all medications securely out of reach of pets. Use lidocaine preparations only as directed by a veterinarian and at the prescribed dosage. Ensure your pet cannot lick treated skin areas.
- What alternative pain relievers are safer for pets than lidocaine?
Various veterinary-approved medications are available for pain management in pets, 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 the appropriate pain medication should always be made in consultation with a 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 in dogs is approximately 1–2 hours, while in cats, it can be significantly longer due to their 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. typically takes 4 to 5 times the half-life.
- Can lidocaine poisoning be fatal?
Yes, untreated severe lidocaine poisoning can lead to death due to cardiac arrhythmias, 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 seizures. However, with early detection and adequate treatment, the risk is significantly reduced.
Literature
- Stehr, S., Christ, T. (2017). Local Anesthetics and Lipid Rescue. In Praxis der Anästhesiologie (pp. 445-456). Springer, Berlin, Heidelberg.
- Fernandez, A. L., Lee, J. A., Rahilly, L., Hovda, L., Brutlag, A. G., Engebretsen, K. (2021). The use of intravenous lipid emulsion 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. in veterinary toxicology. Journal of Veterinary Emergency and Critical Care, 31(2), 173-188.
- Kaplan, A., Whelan, M. (2022). 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: Clinical manifestations, 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 current treatment recommendations. Veterinary Clinics of North America: Small Animal Practice, 52(3), 703-718.
- Martin-Flores, M., Campoy, L. (2019). Local and regional anaesthetic techniques for small animals: A review of current literature and clinical applications. The Veterinary Journal, 246, 55-65.
- Posner, L. P., Burns, P. (2021). Update on local anestheticAn anesthetic is a drug used to induce insensitivity to pain. There are various forms, including local, regional, and general anesthetics, depending on their method of application and desired effect. 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 veterinary patients. Veterinary Clinics of North America: Small Animal Practice, 51(4), 945-963.
- Sanchis-Mora, S., Pelligand, L. (2020). Pharmacokinetic and pharmacodynamic considerations for the use of local anaesthetics in small animals. The Veterinary Journal, 260, 105464.
- Löwe G, Löwe O. Poisoning in Dogs and Cats – A Veterinary Guide. 2nd edition. Kreuztal: Kynos-Verlag. 2021; 208 p.