Changing patterns of chloroquine resistance make malaria prevention increasingly challenging.
Chloroquine alone is now inadequate for prophylaxis in most areas.
Mefloquine is the leading agent for many areas but concerns have arisen about serious neuropsychiatric side effects, which occur rarely, perhaps in one in 10,000 patients. Other side effects such as gastrointestinal and mild mood disorders prompt about 3 percent of patients to discontinue therapy. The leading alternative agent, doxycycline, is almost as effective as mefloquine but has a higher incidence of side effects. Primaquine can be used for prophylaxis of Plasmodium falciparum. Travelers should be advised that most prophylactic regimens require continuation of therapy for four weeks after leaving an endemic area.