Medicine Name: Retense OD Tablet ER. Composition: Flupirtine (400mg). Side Effects: Fatigue Dizziness Nausea Dryness in mouth Tremors Heartburn Vomiting Abdominal pain Constipation Loss of appetite Depression Headache Abdominal discomfort Sleep disturbance Increased sweating Restlessness Nervousness Flatulence Diarrhea.