Lariam contains the active ingredient mefloquine, which is a type of medicine called an antimalarial. It is used in both the prevention and treatment of malaria.
Malaria is a potentially fatal disease caused by various types of parasites known as Plasmodium. Plasmodium are carried by mosquitoes and injected into the bloodstream during a bite from an infected mosquito. Once inside the blood the parasites travel to the liver, where they multiply. The parasites are then released back into the bloodstream where they invade the red blood cells and multiply again. An actual attack of malaria develops when the red blood cells burst, releasing a mass of parasites into the bloodstream. The attacks do not begin until a sufficient number of blood cells have been infected with parasites.
Mefloquine works by attacking the parasites once they have entered the red blood cells. It kills the parasites and prevents them from multiplying further.