Less serious side effects include: 1  Loss of appetite. 2  Weight loss. 3  Nausea. 4  Vomiting. 5  Diarrhea. 6  Frequent urination. 7  Muscle cramps, painful and swollen joints. 8  Excessive tiredness. 9  Difficulty falling asleep. 10  Headache, nervousness, dizziness. 11  Depression, mood swings. 12  Vivid dreams.
Nausea can occur in dogs for many reasons, particularly when the digestive tract and nervous systems are out of balance. Stress can certainly play a role in nausea.
Poisoning with pain medications is common. Aspirin, paracetamol (acetaminophen, Tylenol), ibuprofen (Advil), and naproxen (Aleve) can all cause severe clinical signs in dogs, including vomiting blood, diarrhea, and abdominal pain.