Periwinkle Poisoning in Dogs

The periwinkle, or Catharanthus roseus, is a popular flowering plant used for ground cover, decorative houseplants, and garden plants. The lush green leaves are intertwined with flowers of a purple and bluish mixture of color. This evergreen plant is hardy and grows in many areas of the country throughout the year, with the flowers blooming from the months of April to May; a few variations of the periwinkle will bloom in the fall as well. 

Although there are approximately 30 varieties of the periwinkle plant, the Madagascar periwinkle is the type of periwinkle that contains vinca alkaloids. These naturally occurring compounds are used to treat a variety of illnesses such as high blood pressure and diabetes. The vinca alkaloids known as vinblastine and vincristine are widely used in chemotherapy to treat a variety of cancers in humans and animals. Since this periwinkle contains these alkaloids, if ingested by dogs, they can be poisonous and cause a variety of side effects.

Periwinkle poisoning in dogs occurs when dogs ingest all or part of the Madagascar periwinkle plant. This type of periwinkle plant contains vinca alkaloids which may cause illness and require the attention of the veterinarian.

If your dog has ingested Madagascar periwinkle, it can cause a rapid drop in his blood pressure. Other symptoms include:

• Depression
• Incoordination
• Diarrhea
• Vomiting
• Seizures (severe poisoning)
• Tremors (severe poisoning)
• Hypotension
• Agitation

Types

There are many varieties of periwinkle, and not all of them are toxic. The toxic varieties of periwinkle have alternate names. Other names of the toxic periwinkle known as Madagascar periwinkle include:

• Cape periwinkle
• Ammocallis rosea
• Catharanthine
• Catharanthus
• Catharanthus roseus
• Pink periwinkle
• Pervenche rose
• Old maid
• Lochnera rosea
• Magdalena
• Myrtle

The cause of toxicity from the Madagascar periwinkle is from the ingestion of the plant. Specific causes of poisoning include:

• The toxic alkaloids within the plant, vincristine and vinblastine
• These alkaloids bind to cellular mircrotubules, preventing the cells from dividing
• Inhibits blood vessels from growing
• Inhibits microtubule formation

If you suspect your dog has consumed Madagascar periwinkle, it will be quite helpful to the veterinarian to make the diagnosis of Madagascar periwinkle poisoning in dogs if you are able to take a piece or all of the plant in with you to the appointment.

The veterinarian will do a complete examination, which will include a biochemistry profile, blood testing, and urinalysis. By looking at the test results, the veterinarian will be focusing on the condition of the dog’s internal organs, namely the liver and kidney functions. The veterinarian may also want to see a sample of the dog’s stool to check for any excess plant material.

The veterinarian is trained to look at the dog’s clinical signs, as well as the test results, and make a diagnosis of toxicity of periwinkle. He will also be looking for elevated white blood cell count and any indications of the suppression of bone marrow, as this is one of the common internal signs of this type of toxicity. Other tests that may be performed are tests of the peripheral nerve in the functionality of the muscles (electrodiagnostic testing), and a test to check for the velocity of nerve conduction.

Madagascar periwinkle poisoning is rarely severe and there is no antidote to counteract any of the toxicity. Treatment methods include:

Emesis

If your dog has not self-vomited, the veterinarian will induce vomiting by giving your dog a small dose of hydrogen peroxide. Emesis will help your dog remove any of the plant material from his stomach. The veterinarian may follow-up with activated charcoal to prevent the poison from being absorbed into the gastrointestinal tract.

Medication

In order to ease the irritability of the gastrointestinal tract, the veterinarian may give your dog a medication to relieve any discomfort. Kapectolin may be given up to four times daily to help coat the stomach lining. Sucralfate may also be given; it forms a paste with the acids within the stomach which helps to form a barrier between the stomach and the stomach contents. 

IV Fluids

The vomiting and diarrhea that your dog may be having may cause dehydration. IV fluids will help your dog maintain a healthy level of hydration while he is expelling the plant material. Furthermore, if your dog is constipated, the veterinarian may administer a laxative, which in turn will require fluids to keep him hydrated.

If your dog suffered from Madagascar periwinkle poisoning, his prognosis will be good. The veterinarian will want to keep him for as long as it takes to monitor his progress. Each dog’s recovery time is different, and once the veterinarian feels your dog is able to go home he will give you specific instructions to follow in order for you to monitor him at home.

If your companion suffered from moderate or even severe gastrointestinal tract upset, the veterinarian may prescribe a specific diet for him to be on for a few days. He will give you advice on any foods that you need to feed him, as well as any foods for you to avoid. Your veterinarian may want to see your dog in a few days for a return visit in order to check for proper recovery. If your dog develops any symptoms while at home, it is important to contact your veterinarian with any questions or concerns.