Patients that buy Symmetrel online should be aware of the possible side effects. Some mild adverse reactions that can be experienced are dizziness, insomnia, abnormal dreams, nausea, dry mouth, diarrhea, loss of appetite, dry nose, constipation, headaches, nervousness, or a loss of coordination. More serious side effects can include the following: breathing difficulties, abnormal weight gain, mood changes, hallucinations, thoughts of suicide, a decrease in urination, pronounced fevers, involuntary muscle movements, abnormal heartbeat, and stiff muscles. These side effects should be reported to your local physician as soon as possible.