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.
It is not a nausea medication, rather it helps to normalize a critical process called apoptosis in the body. Mirtazapine is a very effective appetite stimulant. This is particularly useful in cases of canine cancer, especially if either chemotherapy or the cancer itself is causing a loss of appetite.