Vinca Poisoning in Dogs

The Vinca genus of plants is a group of herbaceous plants with trailing stems and five-petaled purple or white flowers. They are referred to as periwinkle, along with the plants in the Catharanthus genus of plants. These plants are often used as an easily maintained ground cover and as an ornamental plant. They contain vinca alkaloids, which are utilized in the production of the cancer treating medications vincristine and vinblastine but may cause a drop in blood pressure when consumed in moderate amounts and paralysis and death when ingested in excessive quantities. The catharanthus rosea also contains these vinca alkaloids, and until recently was known as the vinca rosea.

Vinca alkaloids, found in the Vinca genus of plants, may cause a drop in blood pressure in moderate amounts and paralysis and death in excessive doses.

In many cases, the symptoms from ingesting this plant will be restricted to the gastrointestinal symptoms of vomiting, diarrhea, and abdominal pain accompanied by a slightly lowered blood pressure. Large doses are rare due to the unpalatability of the plant, but can result in more severe reactions and should be addressed by a veterinary professional.  

• Abdominal pain
• Coma
• Death 
• Depression
• Diarrhea
• Lack of coordination
• Lethargy
• Lowered blood pressure
• Seizures
• Tremors
• Vomiting

Types

There are several varieties of the vinca genus plant. The most commonly cultivated varieties of vinca include vinca minor and vinca major. 

Vinca major - Vinca major is a trailing vine also known as greater periwinkle or big leaf periwinkle and grows up to ten inches tall. It has hairy petioles connecting the leaves to the stems, and the one and a half to two-inch flowers bloom from early spring all the way to autumn. 

Vinca minor - Vinca minor is also trailing vine, but there is no hair on the petioles, and the flowers are somewhat smaller, measuring from just a quarter of an inch to one and a half inch in diameter. It is more commonly known as lesser periwinkle and dwarf periwinkle.

Plants in the Vinca genus produce vinca alkaloids that have been used to synthesize cytotoxic drugs that work on cancer cells by inhibiting their ability to divide. The major component, vinblastine, when used in therapeutic doses, is toxic to the white blood cells, but causing bruising and bleeding, and can cause chest pains. Vincristine is also found in this plant, and it is a powerful ally against cancer as it can destabilize the tubulin that cancer requires to grow. This is the alkaloid that is responsible for the nervous system toxicity at high doses.

If you see your pet ingesting any part of a vinca plant, bring your dog to the clinic, where the veterinary team will begin diagnostics. If your canine ate what you believe to be a periwinkle plant, but you are not entirely certain of the plant's identification it may be prudent to transport both your pet and a sample of the remaining plant material to the nearby veterinary clinic.  A biochemistry profile, urinalysis, and (CBC) complete blood count are likely to be requisitioned at this time, as will assessments to check the functionality of the heart. Be sure to inform the veterinarian of recent dietary changes or additional supplements that you may be administering to your companion.

Initial therapy for vinca ingestion will be determined by the length of time since plant material was ingested and which symptoms are presenting. If only a small amount was swallowed, your veterinarian might give you home instructions, which may include information on how to safely induce vomiting for your canine. If the plant is unknown when you call in, or if the amount consumed was moderate to large, your dog’s doctor may request that you bring your pet into the clinic. If the periwinkle plant was ingested recently, within about an hour or two, vomiting is likely to be induced to prevent the absorption of vinca alkaloids into the bloodstream. Activated charcoal is frequently dispensed to the patient as well, in an attempt to soak up as many of the alkaloids as possible. 

In situations in which considerable quantities have been consumed, your dog's doctor may choose to eliminate as much of the plant material from the patient’s stomach as possible by performing a gastric lavage. There is no antidote to intoxication by vinca, however, supportive measures can greatly improve the prognosis, even in extreme cases. Additional supportive treatment generally includes IV fluids for dehydration as well as mixtures of electrolytes and sugars to adjust for any imbalances. The heart and blood pressure will need to be carefully monitored until the toxins have fully cleared the system.

Cases of severe toxicity due to ingestion of plants in the Vinca genus are rare due to the unpleasant taste. Most of the symptoms from eating small to moderate amounts of the periwinkle plant will dissipate within 24 hours. If the symptoms or the quantities ingested necessitate a stay at the veterinary hospital, the recovering patient should have a calm and quiet environment to return home to in order to speed recovery. Anesthesia is often given to facilitate gastric irrigation and may cause short-term difficulties with coordination, and in that case, your dog may be disoriented and  confused when he first returns home.