Klacid XL tablet contains 500 mg of the active ingredient clarithromycin. Klacid belongs to a group of medicines called macrolide antibiotics. Antibiotics stop the growth of bacteria (bugs) which cause infections.Klacid XL tablets are used to treat infections such as: 1.Chest infections such as bronchitis and pneumonia 2.Throat and sinus infections 3.Mild to moderate skin and tissue infections e.g. cellulitis folliculitis or erysipelas. Klacid XL Tablets are used in adults and children 12 years and older.