There are a number of medications that can help prevent or interrupt malaria in travellers to places where infection is common. Many of these medications are also used in treatment. In places where "Plasmodium" is resistant to one or more medications, three medications—mefloquine, doxycycline, or the combination of atovaquone/proguanil ("Malarone")—are frequently used for prevention. Doxycycline and the atovaquone/proguanil are better tolerated while mefloquine is taken once a week. Areas of the world with chloroquine-sensitive malaria are uncommon. Antimalarial mass drug administration to an entire population at the same time may reduce the risk of contracting malaria in the population.