Antidepressants
Definition
Antidepressants are medications widely used in human medicine to treat depression, anxiety disorders, and other mental health conditions. They include different substance groups, such as selective serotonin reuptake inhibitors (SSRIs, e.g., sertraline, fluoxetine), tricyclic antidepressants (TCAs, e.g., amitriptyline), serotonin–norepinephrine reuptake inhibitors (SNRIs, e.g., venlafaxine), and monoamine oxidase inhibitors (MAO inhibitors). Because they are increasingly common in households, pets sometimes ingest them accidentally, which can lead to severe poisoning in some cases. Dogs in particular, but also curious cats, are affected. Owners should therefore be aware of the potential risks these medications pose to their pets and take preventive action.
The most important facts at a glance
AntidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning in dogs and cats is a medical emergency that requires swift action. The different classes of antidepressants—tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), serotonin–norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system. reuptake inhibitors (SNRIs), and monoamine oxidase inhibitors (MAO inhibitors)—can cause different, but potentially life-threatening, poisoning symptoms. TCAs are considered particularly dangerous because of their narrow therapeutic window and effects on multipleMultiple means manifold or repeated and is used to describe conditions or events that occur in multiple instances or at different locations. In veterinary medicine, this may indicate multiple lesions, tumors, or other pathological changes. neurotransmitterNeurotransmitters are chemical messengers that transmit signals from one neuron to the next across the synaptic cleft. They are essential for numerous functions of the nervous system, including mood, sleep, and motor skills. systems.
Symptoms of antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning mainly 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. and the cardiovascular system. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is based on the medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits., the clinical picture, 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. tests such as ECG and laboratory analyses. 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., symptomatic treatment, and intensive monitoring. With early 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 good in most cases. Preventive measures such as safe storage of medications are essential to avoid poisoning incidents.
Causes, development and progression
The most common cause of antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning in dogs and cats is accidentalAccidental means random or unintentional and refers to events or exposures that are not deliberate, such as the accidental swallowing of foreign objects or toxins by dogs and cats. ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of medication that was left out in the open or dropped. Dogs in particular, who often mistake medication for treats, are at high risk. Cats are less commonly affected, but due to their unique metabolism they often react more sensitively.
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 antidepressants 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. even in small amounts. The first symptoms usually appear within one to four hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and often worsen quickly. The course depends heavily on the substance class and the amount ingested. Poisoning with tricyclic antidepressants is often more severe and more life-threatening than poisoning with SSRIs.
Mechanism of action
Tricyclic antidepressants are not very selective, meaning they also interact with other receptors, so a wide range of symptoms can occur in 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..
Their anticholinergic, 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 cardiovascular effects are the main concern.
(anticholinergic = acting against the neurotransmitterNeurotransmitters are chemical messengers that transmit signals from one neuron to the next across the synaptic cleft. They are essential for numerous functions of the nervous system, including mood, sleep, and motor skills. acetylcholine)
In addition, there are many interactions with other medications.
These antidepressants also have a narrow therapeutic window, so 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 occur even after ingesting small amounts.
Antidepressants act on the nervous system through complex mechanisms. They increase the concentration of certain neurotransmitters such as serotonin, norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system., and dopamineDopamine is a neurotransmitter found in various parts of the brain and plays a role in regulating movement, motivation, emotional pleasure, and reward. in the synaptic cleft by blocking their reuptake. This leads to toxic overstimulation of the central and autonomic nervous system.
- Tricyclic antidepressants (TCAs) also block muscarinic, adrenergic, and histaminergic receptors, which can lead 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., a drop in blood pressure, and Convulsions.
- SSRIs and SNRIs primarily cause serotonin overstimulation (“serotonin syndromeA syndrome is a group of symptoms that occur together and indicate a specific disease or condition. A syndrome can be caused by various factors and is often complex in its diagnosis and treatment.”) with neurological and autonomic symptoms.
- MAO inhibitors also indirectly increase serotonin and norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system. levels and can cause dramatic symptoms, especially in combination with other medications.
Supplements
Antidepressants include several drug classes with different targets 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.. In 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. doses, they can cause severe neurological, cardiovascular, and 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. effects in animals. The most common drug groups involved in 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 dogs and cats are:
1. Selective Serotonin Reuptake Inhibitors (SSRIs)
Examples: Fluoxetine, Sertraline, Paroxetine
Mechanism of action:
SSRIs block the reuptake of serotonin (5-HT) from the synaptic cleft, leading to an excessive increase in serotonin concentration.
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In 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. doses → serotonin syndromeA syndrome is a group of symptoms that occur together and indicate a specific disease or condition. A syndrome can be caused by various factors and is often complex in its diagnosis and treatment.:
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Overexcitation of the serotonergic system 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.) and peripheralPeripheral refers to areas located outside the central part of a system or body. In veterinary medicine, this can refer to peripheral nerves, blood vessels, or tissues that are distant from central organs such as the heart or brain.
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Symptoms: tremor, hyperactivityHyperactivity refers to an excessively high level of activity that goes beyond normal behavior. In dogs and cats, hyperactivity can be caused by behavioral problems, neurological disorders, or reactions to medications or toxins., ataxia, Convulsions, 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., 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., mydriasis
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2. Tricyclic antidepressants (TCAs)
Examples: Amitriptyline, Clomipramine
Mechanism of Action:
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Inhibition of the reuptake of norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system. and serotonin
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Anticholinergic effects due to blockade of muscarinic acetylcholine receptorsAcetylcholine receptors are proteins on the surface of nerve and muscle cells that serve as binding sites for the neurotransmitter acetylcholine. They are crucial for the transmission of nerve signals, especially in muscle contraction and in various areas of the nervous system.
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Antihistaminic effect
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Membrane-stabilizing effect on heart muscle cells → risk of 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.
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:
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Cardiotoxicity: QT prolongation, ventricular arrhythmias
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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. symptoms: Convulsions, impaired consciousness
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Anticholinergic signs: mydriasis, 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., dry mucous membranes, urinary retention
3. Serotonin–norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system. reuptake inhibitors (SNRIs)
Examples: Venlafaxine, Duloxetine
Mechanism of Action:
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Increase of serotonin and norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system. 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.)
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In 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. doses also serotonin syndromeA syndrome is a group of symptoms that occur together and indicate a specific disease or condition. A syndrome can be caused by various factors and is often complex in its diagnosis and treatment., 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., neurological symptoms
4. Monoamine Oxidase Inhibitors (MAOIs)
Example: Selegiline (rare)
Mechanism of Action:
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Inhibition of the enzyme monoamine oxidase → reduced breakdown of serotonin, norepinephrineNorepinephrine is a neurotransmitter and hormone that plays an important role in the stress response and in regulating blood pressure and heart rate. It acts similarly to epinephrine, but has specific functions in the nervous system., and dopamineDopamine is a neurotransmitter found in various parts of the brain and plays a role in regulating movement, motivation, emotional pleasure, and reward.
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In 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. doses: massive overstimulation of 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., 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., Convulsions
Symptoms of intoxication
The time between ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and the first signs 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. (latency periodThe latency period is the time between exposure to a disease-causing factor and the appearance of the first symptoms of the disease. At this stage, the disease is present but not yet manifest.) is short. Untreated, deaths in small animals can occur after just one hour.
In both dogs and cats, the antidepressant imipramine can cause signs 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. at an 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. dose of 100 mg/kg body weight.
General symptoms include:
- Dizziness
- Vomiting
- Drowsiness
- 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.
- Lethargy
- Anxiety
- Aggressive behavior
- ConstipationConstipation is another word for infrequent bowel movements where the stool is hard and difficult to pass. In dogs and cats, this can be caused by diet, lack of exercise, or underlying health issues.
- Urinary retention
- Hypokalemia and hyponatremia
Damage to 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. manifests as
- Coordination disorders
- Muscle tremors
- Seizures
- Unconsciousness
In the cardiovascular system
- Pronounced 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.
- Drop in blood pressure leading to
- Cardiogenic shock
Symptoms can vary depending on the drug class but show typical patterns:
Symptoms in dogs:
Tricyclic antidepressants (e.g., amitriptyline):
- ApathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest., lethargy, or severe Restlessness
- Vomiting, DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems.
- Dilated pupils (mydriasis)
- 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. (arrhythmias, 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.)
- Breathing problems, 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. (elevated body temperature)
- Trembling, Convulsions, 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.
SSRI/SNRI (e.g., Fluoxetine, Sertraline, Venlafaxine):
- HyperactivityHyperactivity refers to an excessively high level of activity that goes beyond normal behavior. In dogs and cats, hyperactivity can be caused by behavioral problems, neurological disorders, or reactions to medications or toxins., Nervousness, Restlessness
- Excessive drooling, Vomiting
- Coordination disorders (ataxia), muscle tremors
- Increased heart rate, blood pressure fluctuations
- Convulsions, serotonin syndrome (high Fever, tremor, Restlessness, neurological disorders)
Symptoms in cats:
Cats show similar symptoms but are often more sensitive:
- Drooling, Vomiting, loss of appetite
- ApathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest. or hyperactivityHyperactivity refers to an excessively high level of activity that goes beyond normal behavior. In dogs and cats, hyperactivity can be caused by behavioral problems, neurological disorders, or reactions to medications or toxins., Restlessness
- Neurological symptoms such as ataxia, tremors
- 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., rapid breathing rate
- Rapid development of Seizures, serotonin syndromeA syndrome is a group of symptoms that occur together and indicate a specific disease or condition. A syndrome can be caused by various factors and is often complex in its diagnosis and treatment., 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.
- Rapid deterioration of general condition possible
Diagnosis
The diagnosis of antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning is based primarily on the medical history and the animal’s clinical presentation. Key information includes whether the pet may have had access to antidepressants, as well as the type and amount of the substance potentially ingested. If the historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. is unclear, the characteristic pattern of symptoms can provide clues, with the combination of cardiovascular and 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.) disturbances particularly suggestive of TCA poisoning.
The clinical exam includes assessment of vital parameters, a neurological examination, and cardiovascular evaluation. Laboratory tests such as a complete blood count, 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., and liver and kidney values can indicate organ damage or 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. disturbances. An ECG is especially important for assessing 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., with prolongation of the QRS complex and QT interval being typical of TCA poisoning. In specialized laboratories, toxicology analyses can be performed to detect the specific drug in blood or urine; however, in an emergency these tests are often not available in time.
The differential diagnosisDifferential diagnosis is the process of weighing two or more conditions that cause similar symptoms to determine the specific cause of a patient's symptoms. includes other intoxications / poisonings (e.g., chocolate, xylitol, pesticidesPesticides are chemical or biological substances used to control pests, including insects, weeds, and fungi. In dogs and cats, exposure to certain pesticides can be harmful to health and lead to signs of poisoning.), neurological diseases, 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. disturbances, 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 diseases. A thorough 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 combination are therefore crucial for a fast and correct 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., enabling timely initiation of specific 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..
Therapeutic principles
During decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection., the specific 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. symptoms must be taken into account.
Vomiting should not be induced due to possible Seizures and an impaired swallowing reflex.
Activated charcoal and 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. cleansing with Glauber’s salt (sodium sulfate)Glauber’s salt (sodium sulfate), also known as sodium sulfate, is a naturally occurring salt used as a laxative. In dogs and cats, it can be used to treat constipation or to empty the bowels before diagnostic procedures. are indicated. 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. can also be administered several hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems., and repeatedly at intervals.
Gastric lavage can likewise still be helpful after 3–4 hours, as 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. is associated with slowed 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. passage / transitPassage refers to the passage / transit or transport of substances through the body or within body cavities and channels, such as the digestive tract or airways..
If (suspected) larger amounts or sustained-release formulationsSustained-release formulations are drug formulations that release the active ingredient in a delayed or controlled manner to achieve a more even or prolonged effect. They are useful in the treatment of chronic diseases in dogs and cats. were ingested, endoscopic removal of tablets may also be possible.
There is no specific antidote; however, physostigmine can be used to treat the anticholinergic component in both dogs and cats. 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. bicarbonate is very helpful in treating 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. by correcting 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..
Lipid infusions are also indicated.
Otherwise, 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. As with all intoxications / poisonings, stabilizing vital functionsVital functions are essential bodily functions necessary to sustain life. These include breathing, heart rate, blood pressure, body temperature, and level of consciousness. is the top priority.
Vital functions, especially cardiovascular function, must be closely monitored and rhythm disturbances treated.
Kidney function (diuresisDiuresis is the increase in urine excretion by the kidneys. It is a natural process for removing excess water and waste products from the body.) is stimulated and confirmed urination is monitored.
At the same time as infusion 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 monitor kidney function, the acid-base balanceThe acid-base balance refers to the equilibrium between acids and bases in the body, which is important for maintaining the physiological pH in the blood and other bodily fluids. Imbalances can lead to serious health problems. disturbance—characterized by acidosis—can be treated with 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. bicarbonate.
Seizures must be stopped with medication.
Monitoring body temperature is also necessary.
Supplement
In antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning, rapid action is necessary:
Immediate Measures:
- Induce Vomiting (only within the first hour and only after consulting the veterinarian)
- Administration of activated charcoalActivated charcoal is a fine-pored, highly adsorbing material commonly used in veterinary medicine to treat poisoning. It binds toxins in the gastrointestinal tract to prevent their absorption into the body. to reduce toxinA toxin is a poison produced by living cells or organisms that can be harmful to the body upon contact or ingestion. Toxins can originate from bacteria, plants, animals, or fungi. absorptionAbsorption refers to the uptake of substances by living cells or tissues. In the context of veterinary medicine, it often refers to the absorption of nutrients, drugs, or toxins from the digestive tract into the bloodstream. from the intestines (very effective for antidepressants)
Supportive therapy:
- Infusion 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. (intravenous) for circulatory stabilization and faster 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 toxins
- Control of neurological symptoms (benzodiazepines, e.g., diazepam for Seizures and severe Restlessness)
- Cardiovascular stabilization: ECG monitoring, administration of antiarrhythmics (e.g., lidocaine for severe arrhythmias)
- Temperature control (cooling for 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.)
- SedationSedation refers to the state of calming or suppressing the central nervous system with medication, which reduces anxiety and irritability and sometimes induces a light sleep. to control severe Restlessness or neurological symptoms
- Intensive monitoring of vital parameters required
Severe poisonings often require inpatient intensive care.
Prognosis & follow-up care
The prognosis is very good.
The prognosis for antidepressant poisoning depends largely on several factors: the drug class and amount ingested, the time between ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. and start of treatment, and the animal’s general health status before the poisoning. With early and appropriate treatment, the prognosis is good to very good in most cases. The first 24–48 hours are critical, as life-threatening complications such as severe 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., Convulsions, or RespiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. paralysis can occur.
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. poisoning phase has been overcome, careful follow-up is important. This includes check-ups to assess organ function, especially the heart, liver, and kidneys. A follow-up ECG should be performed to detect possible persistentPersistent means lasting or continuing for an extended period. In veterinary medicine, it can refer to chronic diseases or symptoms that do not subside. 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.. In animals that showed severe neurological symptoms, a neurological follow-up exam is advisable to identify possible residual damage.
Owners should be given detailed instructions for monitoring their pet at home. This includes recognizing warning signs such as renewed lethargy, Coordination disorders, loss of appetite, or Behavioral changes, which may indicate delayed complications. Preventive measures to avoid repeat poisoning cases must be discussed, including storing medications securely in locked cabinets and disposing of spilled tablets immediately.
Research outlook
Research in the field of antidepressant toxicology in small animals is continuously evolving. Current studies focus on optimizing treatment protocols, especially for newer antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. classes. Lipid infusion therapy, originally developed to treat local anesthetic poisoning, is showing promising results for treating poisoning with lipophilic antidepressants and is increasingly being integrated into veterinary emergency protocols.
Molecular biology research approaches are examining genetic factors that influence sensitivity to antidepressants. The MDR1 genetic defectA genetic defect is an abnormality or mutation in the DNA sequence of a gene that can lead to a malfunction or absence of a protein. Genetic defects can cause various genetic diseases and conditions., which occurs in certain dog breeds such as Collies, is a major focus because it impairs the blood-brain barrierThe blood-brain barrier is a protective barrier between the blood vessels in the brain and the brain tissue. It prevents most substances in the bloodstream from entering the brain tissue, but allows nutrients and oxygen to pass through. and can lead to increased toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. of certain medications. Genetic testing could help identify particularly at-risk animals in the future.
New antidotes and specific treatment approaches are being researched to improve 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. for antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning. For example, specific serotonin antagonists are being investigated to treat serotonin syndromeA syndrome is a group of symptoms that occur together and indicate a specific disease or condition. A syndrome can be caused by various factors and is often complex in its diagnosis and treatment. in SSRI poisoning. The development of faster and more precise detection methods for antidepressants in biological samples could also improve diagnosis and treatment in the future.
Frequently asked questions (FAQs)
- Which antidepressants are most dangerous for pets?
Tricyclic antidepressants such as amitriptyline and imipramine are considered particularly toxic to dogs and cats, as they can cause severe cardiovascular and neurological symptoms even in low doses. - How quickly do poisoning symptoms appear after antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems.?
The first symptoms can appear as early as 30 minutes to 3 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems.. With sustained-release preparations, however, symptom onset may be delayed. - Can my pet suffer permanent damage from antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning?
With early and appropriate treatment, the risk of permanent damage is low. However, severe poisonings can lead to permanent neurological or cardiac damage. - Can I induce Vomiting in my pet if it has ingested antidepressants?
Vomiting should only be induced after consulting a veterinarian, as antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning carries a risk of Seizures and aspiration pneumonia. - Are antidepressants also used in veterinary medicine?
Yes, certain antidepressants like clomipramine and fluoxetine are used in veterinary medicine to treat behavioral disorders, but in specially adapted dosages. - Are certain pet breeds or species more susceptible to antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning?
Dog breeds with an MDR1 genetic defectA genetic defect is an abnormality or mutation in the DNA sequence of a gene that can lead to a malfunction or absence of a protein. Genetic defects can cause various genetic diseases and conditions. (e.g., Collies) may react more sensitively to certain medications. In general, smaller animals are at higher risk at the same ingested amount because of their lower body weight. - What should I do if I suspect my pet has ingested antidepressants?
Contact a veterinarian or a veterinary emergency clinic immediately. If possible, note the name of the medication, the dosage, and the number of tablets that may have been ingested. - How long does my pet need to be monitored after antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning?
Intensive veterinary monitoring is required for at least 24–48 hours, as delayed complications can occur. - Can over-the-counter herbal antidepressants like St. John’s Wort also be dangerous for animals?
Yes, even herbal preparations like St. John’s Wort can cause undesirable effects in animals, including increased photosensitivity and interactions with other medications. - How can I prevent antidepressantAn antidepressant is a class of medication used to treat depression and other mood disorders. They work by altering the chemistry in the brain, particularly neurotransmitters like serotonin and dopamine. poisoning in my pet?
Store all medications in locked cabinets out of reach of pets. Make sure no tablets fall on the floor, and dispose of unused medications properly.
Literature
- http://toxdocs.de/2018/intoxikationen-mit-trizyklischen-antidepressiva/
- Löwe G, Löwe O. Notfälle bei Hund und Katze – Ein tierärztlicher Ratgeber. 2. Auflage. Kreuztal: Kynos-Verlag. 2021; 208 p.
- Gwaltney-Brant, S. M. (2021). Antidepressant Toxicosis. In: Veterinary Toxicology: Basic and Clinical Principles. 3rd Edition. Academic Press, pp. 489-498.
- Wismer, T. A. (2019). Antidepressant Poisoning in Small Animals. The Veterinary Clinics of North America: Small Animal Practice, 49(3), 567-581.
- Fernandez, A. L., Lee, J. A., Rahilly, L., Hovda, L., Brutlag, A. G., & Engebretsen, K. (2022). The use of intravenous lipid emulsion therapy in veterinary toxicology. Journal of Veterinary Emergency and Critical Care, 32(1), 5-21.
- Pöch, G., Dittrich, P., & Holzmann, S. (2020). Toxicology of antidepressants in small animals: clinical signs, diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., and treatment. Journal of Veterinary Pharmacology and Therapeutics, 43(5), 385-395.
- Kook, P. H., Quante, S., & Reusch, C. E. (2020). Pharmacological treatment of behavioral disorders in dogs and cats. The Veterinary Journal, 261, 105463.