Vinca major
Apocynaceae
Blue Periwinkle; Bigleaf Periwinkle; Large Periwinkle; Greater Periwinkle; Periwinkle; Running Myrtle; Vinca; Vinca major
Vinca alkaloids and related indole alkaloids, including vindoline, vincadifformine, vincaleukoblastine or vinblastine, 22-oxovincaleukoblastine or vincristine, reserpine, perivincine, vincamine, akuammine, alstonine, leurocristine, ajmalicine, vinine, vinomine, vinoxine, vintsine, leurosine, saponins, and other naturally occurring plant compounds.
Gastrointestinal upset, vomiting, diarrhea, abdominal discomfort, hypotension or low blood pressure, possible cardiac abnormalities, depression, lethargy, incoordination, tremors, seizures, progressive weakness, progressive paralysis, coma, and death in severe cases. Serious intoxication of animals is exceedingly rare, and fatal intoxications appear rarer still, but large ingestions should be treated seriously because Vinca alkaloids can affect blood pressure, neurologic function, and cardiovascular stability.
Vinca major, more commonly known as Bigleaf Periwinkle, Large Periwinkle, Greater Periwinkle, and Blue Periwinkle, is an evergreen trailing vine that spreads along the ground, rooting at the nodes to form dense masses of groundcover. It is noted for being an extremely fast-growing plant, so much so that a single specimen can cover an area of 15 feet or more with a dense carpet of shiny, dark green foliage in just a couple of months.
The leaves are 2 to 3 inches long, oval or heart-shaped, and grow in pairs opposite each other along the length of the stem. The flowers, borne singly in the leaf axils on ascending stems, are blue-violet, funnel-shaped, five-petaled, and approximately 2 inches across. Big Periwinkle flowers heavily throughout the spring and then sporadically during the summer. Because of its fast growth, attractive foliage, and flowering habit, it has long been cultivated as an ornamental groundcover.
Information regarding the specific toxicity of Vinca major varies from source to source, although all sources generally agree that plants in this group contain an extensive array of alkaloids. They also contain saponins and various other compounds. The alkaloid content appears to vary from region to region, especially between areas where the plant grows as an annual rather than a perennial, and between individual plants, growing conditions, and plant parts.
Of the more than 130 compounds identified in Vinca major and related Vinca plants, the principal components include vindoline, vincamine, and vincadifformine. Many of the alkaloids, including akuammine, perivincine, reserpinine, and vinine, are hypotensive, although the extent to which each contributes to clinical poisoning in companion animals is not fully understood. When ingested, the overall concern is a reduction in blood pressure and, in exceptionally large doses, possible neurologic depression, systemic weakness, paralysis, coma, or death.
The broader Vinca and Periwinkle toxicology literature can be confusing because several plants share the common name “periwinkle,” and not all references use the same botanical name. ASPCA lists Periwinkle/Vinca as toxic to dogs, cats, and horses, with Vinca alkaloids as the toxic principle and clinical signs including vomiting, diarrhea, low blood pressure, depression, tremors, seizures, coma, and death. Pet Poison Helpline likewise describes Periwinkle as containing toxic alkaloids, including compounds such as vincristine and vinblastine, and notes that ingestion may cause hypotension, incoordination, tremors, and seizures.
It should be noted, however, that serious intoxication of animals from Vinca major appears to be exceedingly rare, and fatal intoxications appear rarer still. Large ingestions are uncommon because most animals consider the plant to be unpalatable. Despite the plant’s widespread use as a flowering ornamental groundcover, there have been very few reports of intoxication associated with its ingestion by livestock or pets.
The University of Arkansas Division of Agriculture has noted that Periwinkle plants can cause systemic toxicity varying from mild abdominal cramping to serious cardiac complications. That statement, however, is generally directed toward human ingestion of the plant, not ordinary pet or livestock exposures. Human cases may be more severe because people may intentionally ingest larger amounts of the plant in various forms, preparations, or concentrations for medicinal or holistic purposes, whereas animals are more likely to avoid the plant due to its lack of palatability.
For pets and livestock, the practical risk is therefore a combination of the plant’s real alkaloid content and the animal’s likelihood of consuming enough to matter. A small nibble may cause vomiting, diarrhea, or temporary gastrointestinal upset. A larger ingestion, especially in a small animal, medically fragile pet, or animal with existing cardiovascular or neurologic issues, deserves more caution because of the potential for low blood pressure, tremors, seizures, progressive weakness, or cardiac irregularity.
As with many mildly to moderately toxic ornamental plants, the safest approach is to prevent access. Blue Periwinkle should not be treated as an edible groundcover for pets, and dogs or cats that chew landscape plants should be kept away from dense mats of Vinca major, especially newly planted areas, cuttings, clippings, or piles of removed groundcover where plant material is easily accessible.
Immediate Response to Blue Periwinkle Ingestion
- Remove the Source: Prevent further ingestion by removing the pet from the plant, groundcover bed, clippings, vines, leaves, flowers, or any area containing Blue Periwinkle or other Vinca plants.
- Remove Plant Material from the Mouth: If ingestion was recent and it is safe to do so, remove visible plant material from the mouth and flush the mouth thoroughly with water.
- Identify the Exposure: Determine whether the animal chewed leaves, stems, flowers, cuttings, dried material, or an unknown amount, and whether the exposure involved a single nibble or repeated chewing over time.
- Watch for Early Signs: Monitor for vomiting, diarrhea, abdominal discomfort, depression, lethargy, reduced appetite, incoordination, weakness, tremors, or abnormal behavior.
- Watch for Cardiovascular or Neurologic Signs: Low blood pressure, collapse, severe weakness, tremors, seizures, progressive paralysis, coma, or possible cardiac abnormalities should be treated as emergency signs.
- Contact Veterinary Help: Consult a veterinarian, emergency veterinary clinic, ASPCA Animal Poison Control, or Pet Poison Helpline if a large amount was ingested, if symptoms are present, if the amount is unknown, or if the exposed animal is a cat, dog, horse, small animal, young animal, elderly animal, pregnant animal, or medically fragile animal.
Inducing Vomiting and Decontamination
- Getting Plant Material Out Matters: If a dog has recently swallowed Blue Periwinkle, removing remaining plant material from the stomach may reduce continued exposure to Vinca alkaloids and other irritant compounds. In appropriate dog exposures, vomiting may be one of the least disruptive ways to remove recently ingested plant material before more toxin is absorbed.
- Inducing Vomiting in Dogs Only: If ingestion was recent and the dog is alert, breathing normally, able to swallow, and not showing weakness, collapse, tremors, seizures, severe depression, repeated vomiting, low blood pressure, cardiac signs, breathing difficulty, or neurologic signs, a veterinarian or animal poison-control professional may recommend inducing vomiting with fresh 3% hydrogen peroxide.
- Cat Warning: Hydrogen peroxide should not be used to induce vomiting in cats unless a veterinarian specifically directs it. Cats are more prone to irritation and complications from hydrogen peroxide, and home vomiting attempts may create more risk than benefit.
- Do Not Induce Vomiting in an Unstable Animal: Vomiting should not be attempted in any animal that is weak, collapsed, sedated, having trouble breathing, unable to swallow normally, already vomiting repeatedly, showing neurologic signs, showing cardiac signs, or otherwise unstable.
- Activated Charcoal: Activated medical charcoal may be useful in binding ingested alkaloids or plant compounds in the gastrointestinal tract, but it should be administered under veterinary or poison-control direction, especially if the animal is vomiting, depressed, weak, or at risk of aspiration.
Symptomatic and Supportive Care
- No Specific Antidote: There is no specific antidote for ingestion of Periwinkle or Vinca plants, so treatment is generally symptomatic and supportive.
- Hydration: Ensure the pet receives adequate fluids to reduce the risk of dehydration caused by vomiting or diarrhea.
- Blood Pressure Monitoring: Because some Vinca alkaloids may lower blood pressure, animals showing weakness, collapse, pale gums, severe lethargy, or abnormal mentation should be evaluated for hypotension.
- Cardiac Monitoring: Possible cardiac abnormalities should be monitored by a veterinarian, particularly if the animal is weak, collapsed, tremoring, or showing signs of poor circulation.
- Neurologic Monitoring: Tremors, seizures, progressive weakness, paralysis, coma, or abnormal behavior require veterinary attention and supportive treatment.
- Gastrointestinal Protection:
- Kapectolin: To alleviate gastrointestinal upset and diarrhea, Kapectolin may be given at a dose of 1 to 2 ml/kg four times daily to help coat and protect the stomach lining.
- Sucralfate: Sucralfate may be used for gastrointestinal irritation because it reacts with stomach acid to form a paste-like protective barrier between irritated tissue and stomach contents.
- Dogs greater than 60 lbs: 1g every 6 to 8 hours.
- Dogs less than 60 lbs: 0.5g every 6 to 8 hours.
- Cats: 0.25g every 8 to 12 hours.
Prognosis and Recovery
- Most Cases: Serious intoxication of animals is exceptionally rare, and in most cases symptoms are expected to be limited to gastrointestinal upset, including vomiting and diarrhea.
- Expected Recovery: Pets with mild signs and limited ingestion are expected to recover with supportive care once vomiting, diarrhea, and appetite improve.
- Higher-Risk Cases: Prognosis becomes more guarded if the animal develops low blood pressure, collapse, tremors, seizures, cardiac abnormalities, progressive paralysis, coma, or other systemic signs.
- Rare Fatality Risk: Fatal intoxications appear rare, but the plant contains real pharmacologically active alkaloids, and large ingestions should be treated seriously.
- Prevention: Prevent further ingestion of the plant, remove clippings or accessible vines, and keep pets that chew groundcover away from Blue Periwinkle and other Vinca plantings.