Medicine Name: Aten-H 12.5 Tablet. Composition: Atenolol (50mg) + Hydrochlorothiazide (12.5mg). Side Effects: Nausea Headache Fatigue Dizziness Cold extremities Increased blood uric acid Decreased potassium level in blood Glucose intolerance Slow heart rate Decreased sodium level in blood Decreased magnesium level in blood Increased calcium level in blood Increased blood lipid level.