Cerenia (r) is the only FDA-approved medicine for treating vomiting in dogs and cats, as well as preventing vomiting in dogs from motion sickness. It is a non-drowsy drug that comes in two forms: an injection administered by your veterinarian or pills administered at the hospital or at home. Anti-sickness injections are used to prevent or treat nausea and vomiting caused by cancer treatments, surgery, or other illnesses. They work by blocking certain messages between nerves and muscles inside the body. These messages tell the stomach not to digest food and the lungs not to cough up mucus. Without these messages, the dog does not feel sick and therefore is not going to eat or drink enough to be ill. The most common anti-sickness injection used in dogs is called ondansetron. It reduces the feeling of nausea and vomiting over an extended period of time by blocking certain receptors in the brain and spinal cord that would otherwise signal pain and discomfort. Other drugs can be added to ondansetron to target specific problems such as pain, anxiety, restless legs syndrome, urinary incontinence, and diarrhea. Some studies show that ondansetron may cause drowsiness in some dogs. This behavior is usually only apparent after several days of treatment so it should not affect you if your dog takes the drug.