These tablets contain the active ingredient mefloquine. They are used to treat malaria and to help prevent you from catching malaria. Malaria is a life threatening disease and a major health risk for travellers visiting tropical countries. It occurs when small parasites are passed from one person to another by the bites of certain mosquitoes. Mefloquine is especially useful if you are travelling to countries where there is a type of malaria which is particularly difficult to treat.