Antiemetics

Antiemetics are medications that suppress the urge to vomit and prevent vomiting. They are used in dogs when nausea and vomiting occur, due to motion sickness, gastrointestinal problems, side effects of medications, or after surgery. Antiemetics act on the central nervous system and/or the gastrointestinal tract to block the urge to vomit.

When are antiemetics used in dogs?

Antiemetics are used when a dog suffers from severe or persistent vomiting. Common causes:

• Gastrointestinal infections: Bacterial or viral infections can lead to nausea and vomiting.
• Travel sickness: Many dogs suffer from nausea and vomiting when travelling by car or on trips.
• Drug side effects: Chemotherapeutic agents or anaesthetics can cause nausea and vomiting.
• Poisoning: After initial detoxification, antiemetics can help control vomiting.
• Food intolerances: Some dogs react sensitively to certain foods.
• After operations: To prevent postoperative nausea, antiemetics are often administered prophylactically.

How do antiemetics work?

Antiemetics block certain receptors that trigger the urge to vomit. Depending on the cause of the nausea, they act at different points:

• In the central nervous system: They act on the vomiting centre in the brain by blocking receptors that send signals from the stomach and intestines to the brain.
• In the gastrointestinal tract: They regulate stomach movements and reduce inflammation.
• Serotonin antagonists: They block serotonin receptors in the brain and gastrointestinal tract to prevent nausea.

Frequently used antiemetics in dogs

• Maropitant (Cerenia): Blocks neurokinin-1 receptors (NK1) in the brain, which are responsible for triggering vomiting. Effective for travel sickness, chemotherapy and gastrointestinal problems.
• Metoclopramide: Acts in the brain and gastrointestinal tract. Accelerates gastric emptying and prevents reflux into the oesophagus. Frequently used for gastrointestinal disorders or after operations.
• Ondansetron: A serotonin antagonist, mainly used for nausea and vomiting caused by chemotherapy. Blocks serotonin receptors in the gastrointestinal tract and brain.
• Chlorpromazine: A phenothiazine antiemetic that influences the vomiting centre in the brain. Mainly used for severe vomiting due to travel sickness or gastrointestinal disorders.

Side effects of antiemetics in dogs

Antiemetics are generally safe for dogs but can cause side effects in some cases:

• Drowsiness or sedation: Some antiemetics, such as chlorpromazine, can make the dog tired.
• Diarrhoea: Some antiemetics can lead to diarrhoea, as they influence gastrointestinal motility.
• Changes in behaviour: In rare cases, dogs may appear nervous or over-excited after administration.
• Low blood pressure: With certain medications, a drop in blood pressure can occur, particularly in dogs with pre-existing conditions.

If side effects occur, the vet should be informed so that the dosage can be adjusted or a different medication prescribed.