Foxglove (Digitalis Purpurea)
Foxglove (Digitalis purpurea) is a plant native to Europe with characteristic bell-shaped flowers, widely cultivated in gardens. All parts of the foxglove plant contain cardiotonic glycosides, also known as digitaloids or cardenolides, which are highly toxic to dogs and cats. There are about 100 different cardiotonic steroid glycosides in the plant, with digitoxin and digoxin being the most important active ingredients. These substances were formerly used as medications in human and veterinary medicine but are less common today due to the development of more effective and safer alternatives.
The toxicity of foxglove is classified as very high (+++). Even small amounts can lead to life-threatening poisoning in pets. For a medium-sized dog, just five dried leaves are considered potentially fatal. In addition to foxglove, other plants such as lily of the valley (Convallaria majalis) and oleander (Nerium oleander) also contain similar cardiotonic glycosides with comparable toxicity.
It is particularly dangerous that not only fresh or dried plant parts are poisonous, but also the water in vases where foxglove has stood can contain toxic concentrations of the active ingredients.
The most important facts at a glance
Poisoning by foxglove (Digitalis purpurea) is a medical emergency in dogs and cats. The cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. contained in all parts of the plant influence heart function by inhibiting sodium-potassium ATPase, leading to increased heart contraction and slowed conduction. Overdosing results in life-threatening cardiac arrhythmias.
Symptoms initially include 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. complaints such as vomiting and diarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., followed by cardiac symptoms (arrhythmias, 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 neurological abnormalities. Cats are particularly at risk due to their limited 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. capacity, as are dogs with the MDR-1 gene defect.
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 anamnesis, clinical symptoms, and cardiological 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. focuses on decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. using emesis and 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., stabilization of the cardiovascular system, and symptomatic treatment. Unfortunately, a 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. (DigiFab) is not routinely available in veterinary medicine in Germany.
With early 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 cautiously favorable, with follow-up care including regular cardiological check-ups. Preventive measures such as removing 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. plants from the pets’ environment are helpful to avoid poisoning cases.
Causes, development and progression
Foxglove poisoning in pets usually occurs through 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 plant parts. Despite the plant’s bitter taste, which deters many animals, poisoning cases still occur, especially in young, curious animals or those with Pica 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. (pathologicalPathological refers to anything related to diseases or their processes. Pathological changes are those that deviate from the normal structure or function and indicate a disease. eating of non-nutritive substances).
The mechanism of action of cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. is based on the inhibition of sodium-potassium ATPase in cardiac muscle cells. This enzyme is responsible for transporting sodium out of the cell and potassiumPotassium is an essential mineral and electrolyte that is important for the function of nerves and muscles, including the heart muscle. Potassium also helps regulate fluid balance and blood pressure. into the cell. Inhibition leads to an increase in intracellular sodium concentration, which in turn leads to increased calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. influx. The increased calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. concentration causes an increased contractile force of the heart muscle (positive inotropic effect) and slowed conduction in the heart’s conduction system (negative dromotropic effect).
While these effects may be desirable in therapeutic applications for heart failure, in cases of poisoning, they lead to dangerous cardiac arrhythmias. Additionally, the glycosides 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 gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract, which explains the neurological and 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.
Cats are particularly at risk because their limited ability to glucuronidate (an important 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. pathway for detoxification) makes them less able to break down toxins. Dogs with the MDR-1 gene defect, which is more common in Collies and related breeds, also show increased sensitivity to cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions., as the defect impairs 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. excretion.
Mechanism of action
Cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. inhibit specific enzymesEnzymes are biological catalysts that accelerate specific chemical reactions in the body without being consumed. They play a crucial role in virtually all physiological processes. (sodium-potassium ATPases) in heart muscle cells, leading to shifts in electrolyte concentrations (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., potassiumPotassium is an essential mineral and electrolyte that is important for the function of nerves and muscles, including the heart muscle. Potassium also helps regulate fluid balance and blood pressure., calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction.) within the heart muscle cell.
The associated increase in calcium leads to an increase in the contractile force and speed of the heart muscle cell.
Furthermore, cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. slow down nerve conduction in the heart’s nerve pathways, thereby reducing heart rate.
As the concentration of glycosides in the blood increases, the effects intensify.
Additionally, disturbances in the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract 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. occur.
Signs of intoxication, initially affecting only the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract, are observed in dogs and cats at 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 of approximately 2.5 ng/ml.
For dogs, five dried foxglove leaves are considered lethal.
Cats are particularly sensitive to 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. The reason is their severely limited ability to break down certain substances via the glucuronidationGlucuronidation is a metabolic process in which glucuronic acid is bound to substances such as drugs, toxins, or hormones to make them more water-soluble and easier to excrete. This process is important for detoxification in the body of dogs and cats. 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. pathway.
Dogs with the MDR-1 gene defect (Collies, etc.) are also particularly sensitive to 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. concentrations.
Supplements
For dogs and cats, even the ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of small amounts of fresh plant material poses a potentially life-threatening danger.
- Main 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. Substances
The most important cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. in foxglove are:
- Digoxin
- Digitoxin
- Gitoxin
- Digitalin
These substances are lipophilic, well absorbed through the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract, and act directly on cardiac muscle tissue as well as indirectly via the autonomic nervous system.
- Mechanism of Action at the CellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. Level
Cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. competitively inhibit the sodium-potassium ATPase (Na⁺/K⁺ pump) in the cell membrane of cardiomyocytes (heart muscle cells).
A) Primary Effect: Inhibition of Na⁺/K⁺-ATPase
- This pump is essential for maintaining the electrolytic homeostasisHomeostasis is an organism's ability to maintain the internal balance of its bodily environment by regulating physiological processes. This includes controlling temperature, pH value, blood sugar levels, and other vital parameters. of the heart muscle cell.
- Inhibition leads to an increase in intracellular 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. concentration.
- This leads to an inhibition of the Na⁺/Ca²⁺ exchanger, causing calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. to accumulate in the cell.
- The increased intracellular calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. leads to increased contractility of the heart muscle (positive inotropic effect).
B) Secondary Effects
- However, the increased calciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. concentration also leads to electrical instability → cardiac arrhythmias.
- Additionally, vagal tone is increased (parasympathetic activity), which can lead to a slowing of the heart rate (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.).
- 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 of Overdose
The therapeutic window of foxglove glycosides is very narrow; an overdose quickly leads to intoxication. In dogs and cats, the range between effective and 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 is particularly narrow, which is why any 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 plant is considered potentially dangerous.
Main Effects:
- CardiotoxicCardiotoxic describes substances or influences that are harmful to the heart. Cardiotoxic effects can impair heart function and lead to various heart problems.: Arrhythmias (e.g., ventricular extrasystoles, atrial block, AV block), 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. or 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.
- Central nervous: Lethargy, disorientation, in severe cases seizures
- 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.: Vomiting, diarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., hypersalivation – often the first clinical signs
- Specific ToxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. in Dogs and Cats
- Dog: More prone to ingesting larger quantities due to curious behavior (e.g., playing with plant parts). First signs are usually 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. (vomiting, nausea), followed by cardiac arrhythmias and neurological abnormalities.
- Cat: Less frequently affected due to their more selective eating habits, but highly sensitive to cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions.. Even small amounts can cause 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., hypothermia, and massive weakness.
- Summary of ToxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. Mechanisms of Action
| Level of Action | Effect of Foxglove Glycosides |
| CellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. (Heart) | Inhibition of Na⁺/K⁺-ATPase → CalciumCalcium is a mineral that is essential for building and maintaining strong bones and teeth. It also plays a role in blood coagulation, nerve transmission, and muscle contraction. accumulation → increased contraction |
| Electrophysiology | Conduction disturbances, arrhythmias |
| Autonomic Nervous System | Increased vagal tone → 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 |
| GastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. Tract | Direct irritation → Vomiting, DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems. |
| 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. | Disorientation, weakness, possibly seizures |
- Conclusion
Foxglove is one of the most dangerous poisonous plants for dogs and cats. The cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. it contains disrupt ion homeostasisHomeostasis is an organism's ability to maintain the internal balance of its bodily environment by regulating physiological processes. This includes controlling temperature, pH value, blood sugar levels, and other vital parameters. and directly affect heart function by inhibiting Na⁺/K⁺-ATPase. Even tiny amounts of the plant can triggerA trigger is a stimulus that elicits a specific reaction or state. In veterinary medicine, this can refer to emotional responses, such as fear or aggression, or medical conditions, such as seizures in dogs and cats. severe, sometimes fatal, cardiac arrhythmias. Typical symptoms include vomiting, lethargy, slowed pulse, and eventually syncopal events or sudden death.
Symptoms of intoxication
The symptoms of foxglove poisoning typically develop within 2–6 hours after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. of the plant and can be divided into several phases.
In the 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, 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 dominate:
- Increased salivation (hypersalivation)
- Repeated vomiting, often severe
- DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems., which can be bloody in severe cases
- Inappetence and refusal to eat
- AbdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. pain, recognizable by a tense abdominalThe term "abdominal" refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. wall
As poisoning progresses, cardiovascular symptoms come to the forefront:
- Irregular heartbeat (arrhythmias)
- 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. (slowed heartbeat) or 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. (accelerated heartbeat)
- Heart block of various degrees
- Weak pulse
- Pale or bluish mucous membranes
- Collapse and weakness
Neurological symptoms may also occur:
- Gait instability (ataxia)
- Tremors or muscle twitching
- Disorientation
- Seizures
- In severe cases, impaired consciousness leading to comaA coma is a deep state of unconsciousness where an individual cannot be awakened and does not respond to stimuli. In dogs and cats, it can be caused by severe illnesses, poisoning, or neurological problems.
In advanced poisoning, life-threatening complications can occur:
- 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
- pulmonaryPulmonary refers to the lungs or the respiratory system. Pulmonary diseases in dogs and cats include conditions such as Pneumonia, asthma, and pulmonary hypertension. edemaAn edema is a buildup of fluid in the body's tissues, leading to Swelling. Edema can be localized or generalized and is often a sign of an underlying condition.
- Multi-organ failureMultiple organ failure is a serious condition in which several vital organ systems fail simultaneously. In dogs and cats, this can be caused by severe illness, injury, or as a result of toxicity, and is often life-threatening.
- Death
The severity of symptoms correlates with the amount of plant material ingested and the time until treatment. In cats, symptoms may appear more quickly and severely than in dogs due to their particular sensitivity.
Diagnosis
The diagnosis of foxglove poisoning is based on several pillars and requires a careful anamnesis as well as clinical and laboratory diagnostic examinations.
The anamnesis is crucial and should include the following aspects:
- Possible access to foxglove or other cardiac glycoside-containing plants
- Observed ingestion of plant parts
- Time of suspected 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.
- Onset and course of symptoms
The clinical examination focuses on:
- Cardiovascular status (heart rate, heart rhythm, pulse quality, mucous membrane color)
- Neurological status
- Hydration status after vomiting and diarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems.
Laboratory diagnostic measures include:
- Blood count and serumSerum is the liquid part of the blood that remains after coagulation. It does not contain blood cells or coagulation factors, but many other proteins, antibody and electrolytes. Serum is used in diagnostics for a variety of blood tests. chemistry to assess organ function
- 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. (especially potassiumPotassium is an essential mineral and electrolyte that is important for the function of nerves and muscles, including the heart muscle. Potassium also helps regulate fluid balance and blood pressure., as hyperkalemiaHyperkalemia refers to a potassium level in the blood that is too high. Potassium is essential for normal cell function, but an excess can lead to cardiac arrhythmia and other health problems. can occur in severe poisoning)
- Acid-base status
- ECG for detecting cardiac arrhythmias (typical changes include ST segment 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., prolonged PR intervals, AV blocks)
- In specialized laboratories: Detection of digitoxin or digoxin in blood or urine
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 poisonings with cardiotoxicCardiotoxic describes substances or influences that are harmful to the heart. Cardiotoxic effects can impair heart function and lead to various heart problems. effects, primary heart diseases, 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. disorders. Particularly important is the differentiation from poisonings with other cardiac glycoside-containing plants such as oleander or lily of the valley, which can cause similar symptoms.
A definitive 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. can be made by direct detection of cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. in the blood, but these tests are not universally available, and results are often not available quickly enough to influence 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 decisions.
Therapeutic principles
The antidote DigiFab available in human medicine
is not available for veterinary medicine in Germany.
Atropine counteracts some of the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effects of cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. on the heart.
Lidocaine and phenytoin can also be used to treat severe cardiac arrhythmias.
DecontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. is achieved by emptying the stomach 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.. Since cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. are excreted in bile and reabsorbed in the intestineThe intestine is the medical term for the gut, including the small intestine (intestinum tenue) and the large intestine (intestinum crassum). It plays a central role in the digestion and absorption of nutrients. (enterohepatic circulation), 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. should be administered repeatedly.
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. particularly addresses the correction of fluid, electrolyte, and 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. disturbances, as these can enhance the toxic effect of glycosides on the heart.
Treating foxglove poisoning requires a rapid and comprehensive approach. As it is a medical emergency, 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. should be initiated immediately.
DecontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. is the first priority:
- In cases of recent 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. (within 1–2 hours), vomiting can be induced under veterinary supervision, provided the animal is conscious and shows no neurological symptoms.
- 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. under anesthesia for larger ingested amounts or if vomiting is contraindicated.
- 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. (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. 1–4 g/kg body weight) 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.. Since cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. undergo enterohepatic circulation, 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. should be repeated every 4–6 hours for 24–48 hours.
Symptomatic 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. 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:
- 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. to stabilize circulation and promote renal excretion of toxins.
- Correction of electrolyte and acid-base disturbances, especially hyperkalemiaHyperkalemia refers to a potassium level in the blood that is too high. Potassium is essential for normal cell function, but an excess can lead to cardiac arrhythmia and other health problems..
- For cardiac arrhythmias: Antiarrhythmics such as lidocaine or phenytoin.
- Atropine can be used for severe 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., as it counteracts some of the toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effects of cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. on the heart.
- Oxygen therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. for 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. or 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..
- AnticonvulsantAn anticonvulsant is a medication used to prevent or control seizures and other types of neurological disorders associated with abnormal electrical activity in the brain. medications for neurological symptoms.
In human medicine, DigiFab (digoxin-specific Fab fragments) is available as a 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., but it is not routinely available in veterinary medicine in Germany. In severe cases, the use of this 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. can be life-saving and should be considered.
Intensive care monitoring is essential and should be continued for at least 48–72 hours, as toxins are slowly excreted and delayed complications can occur.
Prognosis & follow-up care
As always, the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. depends on the amount of 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. (plant parts) ingested and rapid and comprehensive decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection.. Since cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. taste bitter, there is a high probability that only a small amount of plant material will be ingested.
The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is generally good. Symptoms usually subside within 2–3 days.
The prognosis for foxglove poisoning depends on several factors: the amount of 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. ingested, the time until treatment, the animal’s general health, and the presence of risk factors such as the MDR-1 gene defect in dogs or impaired kidney function.
With early 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 cautiously favorable. Most animals recover completely within 2–3 days if decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. is performed promptly and no severe cardiac arrhythmias have occurred. The fact that cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. taste bitter, and many animals therefore ingest only small amounts, further improves 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..
However, in severe poisoning with pronounced cardiac arrhythmias or neurological symptoms, the prognosis is cautious to unfavorable. 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 higher-grade AV blocks, in particular, can lead to death despite intensive therapy.
Aftercare following 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 includes:
- Regular cardiological check-ups using ECG and echocardiographyEchocardiography is an ultrasound examination of the heart that assesses the structure and function of the heart valves and chambers. It can provide information about heart size, pumping function, and the presence of heart disease., as cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. can also cause delayed or chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. damage to the heart muscle.
- Monitoring kidney function, as toxin excretion occurs via the kidneys and can strain them.
- Dietary adjustments during convalescence, possibly easily digestible food for persistentPersistent means lasting or continuing for an extended period. In veterinary medicine, it can refer to chronic diseases or symptoms that do not subside. 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.
- Strict rest in the first few days after poisoning to spare the cardiovascular system.
In the long term, pet owners should take preventive measures to prevent re-poisoning. This mainly includes removing foxglove and other poisonous plants from the garden or securely fencing off such areas.
Research outlook
Research into foxglove poisoning in pets is continuously evolving. Current studies focus on several areas:
In toxicology, new detection methods for cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. are being developed to enable faster and more precise diagnoses. Point-of-care tests could simplify and accelerate the detection of digitoxin and digoxin in veterinary practice in the future.
In the field of therapy, research is being conducted on improved 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. strategies. The development of veterinary-specific Fab fragments against cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. could revolutionize treatment options. In addition, new formulations 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. are being investigated, which should enable more efficient binding of toxins in the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract.
Genetic studies deal with the differing sensitivity of various animal breeds to cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions.. In addition to the known MDR-1 gene defect, further genetic factors that could influence the metabolism and 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 cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions. are being investigated.
In preventive veterinary medicine, digital tools such as apps for identifying toxic plants are being developed to help pet owners recognize potential dangers in the garden or during walks. In addition, educational measures for pet owners are being evaluated to raise awareness of plant poisonings.
Research into the long-term consequences of survived foxglove poisoning is another important field. This concerns the question of whether and to what extent subclinicalSubclinical refers to a condition or disease that does not yet cause any recognizable symptoms. Subclinical diseases can only be diagnosed by specific tests or examinations. heart damage can occur after a survived poisoning and how this can be detected and treated early.
Frequently asked questions (FAQs)
- How do I recognize foxglove poisoning in my pet?
Look for sudden vomiting, drooling, diarrhea, weakness, irregular heartbeat, and unsteady gait. If you suspect poisoning, seek veterinary attention immediately. - Can I treat poisoning at home?
No, foxglove poisoning is a medical emergency that requires immediate veterinary treatment. Attempts at self-treatment can be dangerous. - Is foxglove poisoning always fatal?
No, with early treatment, many animals have a good chance of survival. However, if left untreated, the poisoning can lead to death from cardiac arrest. - Is foxglove still poisonous when dried?
Yes, the toxins remain active in dried plant parts and can even be more concentrated than in fresh plants. - Which animals are particularly at risk from foxglove poisoning?
Cats and dogs with the MDR-1 gene defect (like Collies) are particularly sensitive. Young, curious animals have a higher risk of eating plant parts. - How long does recovery take after foxglove poisoning?
With successful treatment, symptoms usually subside within 2–3 days. However, full recovery can take 1–2 weeks. - Can I make my garden pet-friendly?
Yes, avoid poisonous plants like foxglove or plant them in fenced areas that your pets cannot access. - Are there breed-specific differences in sensitivity to foxglove?
Yes, dogs with the MDR-1 gene defect (especially Collies, Australian Shepherds, and related breeds) are more sensitive to cardiac glycosidesCardiac glycosides are a class of drugs derived from certain plants that improve the strength and efficiency of heart contractions. They are now produced synthetically. They are used in dogs and cats to treat certain heart conditions.. - Can recovered foxglove poisoning cause long-term damage?
Yes, in some cases, permanent heart damage may remain, which is why regular cardiological check-ups after poisoning are important.
What other plants contain similar toxins to foxglove?
Lily of the valley, oleander, hellebore, and sea onion also contain cardiotonic glycosides and can cause similar poisoning symptoms.
Literature
- Kovalkovičová N, Šutiaková I, Pistl J, et al. Some food 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. for pets. Interdisciplinary Toxicology. 2019;12(1):45-51.
- Plumlee KH. Clinical Veterinary Toxicology. 2nd ed. St. Louis: Mosby; 2020.
- Gupta RC. Veterinary Toxicology: Basic and Clinical Principles. 3rd ed. Academic Press; 2018.
- Poppenga RH, Gwaltney-Brant SM. Small Animal Toxicology Essentials. 2nd ed. Wiley-Blackwell; 2021.
- Löwe G, Löwe O. Poisoning in Dogs and Cats – A Veterinary Guide. 2nd edition. Kreuztal: Kynos-Verlag. 2021; 208 p.