Is Foxglove (Digitalis purpurea)Toxic to Cats

• Family: Scrophulariaceae
• Botanical name: Digitalis purpurea
• Common names: Foxglove, Lady’s glove, Fairy’s glove, Virgin’s glove, Witch’s gloves, Dead man’s bells
• Plant type: Biennial
• Mature size: 1-3 feet tall (30 – 90 cm)
• Toxicity: Toxic to cats, dogs, humans, livestock
• Toxic parts: Flowers, leaves, stems, and seeds
• Severity: Severe
  
• Toxic principle: Cardiac glycosides, including digoxin and digitoxin

Foxglove is a herbaceous biennial or short-lived perennial growing 1-2 metres tall. It is native to  Europe, western Asia, and northwestern Africa but can now be found worldwide. The plant is popular for its attractive tubular pendant flowers which grow in pink, purple, yellow and white.

Queensland Health rates foxglove toxicity as category 1 and 3

Category 1:

Extremely toxic, has been known to cause injury, permanent disability, and in some cases, death. 

Category 3:

Irritant to skin or eyes from sap, prickles, spines or stinging hairs. 

The University of California rates foxglove as toxicity class 1

Major Toxicity: These plants may cause serious illness or death.

Also known as cardenolides of bufadienolides, cardiac glycosides reversibly inhibits the activity of the myocardial NA-K aptase pump, an enzyme that controls the movement of ions into the heart. This induces an increase in intracellular sodium that drives an influx of calcium into the heart and causes an increase in contractibility but slowing conduction between the top (atrium) and the bottom (ventricle) which can lead to fatal arrhythmias (irregular heartbeat).

Digoxin is a medicine derived from cardiac glycosides to treat heart failure in human and veterinary medicine. It works by increasing heart output, which is beneficial in patients with heart failure, atrial fibrillation and atrial flutter, but extremely dangerous in those with a healthy heart.

Clinical signs

All parts of the plant are toxic to cats and even a small amount is enough to cause sickness.

Gastrointestinal:

• Nausea (drooling, loss of appetite)
• Vomiting
• Diarrhea
• Abdominal pain

Cardiovascular:

• Abnormal heart rhythm
• Increased (tachycardia) or decreased heart rate (bradycardia)

Central nervous system: 

• Seizures
• Tremors
• Dilated pupils

Diagnosis

A diagnosis is based on a history of exposure to foxglove, the veterinarian will need to know when ingestion occurred and how much was ingested.

Diagnostic workup:

• Baseline tests: Complete blood count, urinalysis and biochemical profile to evaluate the overall health of the cat and assess kidney function
• Electrocardiogram: To monitor heart rate.
• Echocardiogram: An ultrasound of the heart to monitor how it is functioning.

Treatment

Immediate veterinary treatment is critical if your cat has ingested any part of a foxglove plant, no matter how small. There is no antidote to foxglove poisoning, and treatment is aimed at managing symptoms. If there is still any remaining plant matter in the mouth, remove as much as you can.

Gastric lavage (pump the stomach) if ingestion was recent followed by activated charcoal to bind to any remaining toxin in the gastrointestinal tract which prevents further absorption.

Intravenous fluid therapy will be initiated to correct electrolyte imbalances and manage hypotension (low blood pressure).

Heating pads will be placed under the cat as a sudden drop in body temperature is common.

Additional supportive therapy may include antiemetics to control vomiting.

Are there any other plants that contain cardiac glycosides?

Yes, the following plants also contain cardiac glycosides:

• Oleander
• Lily of the valley
• Milkweed

Prevention

The only way to prevent foxglove exposure is to not grow them in your garden if you have children or pets. Exposure can occur if the cat ingests any part of the plant, or brushes past it and later grooms.

If you have had dermal (skin) exposure, wash your hands before eating and touching your cat.