Increased international travel to areas where malaria is endemic and increasing drug resistance are putting a growing number of travelers at risk for contracting malaria. Kain and colleagues reviewed current recommendations for chemoprophylaxis of malaria in travelers and discussed some newer regimens for use in resistant areas.
Malaria risk is widespread in Mexico, Central America, South America, Africa, the Middle East, and Asia. Chloroquine is the drug of choice for people who travel to these areas; however, resistance to chloroquine is now widespread in all areas of the world where malaria is endemic, but it is still an effective choice for prophylaxis in travelers to Mexico, the Caribbean, Central America, Argentina, and parts of the Middle East and China Mefloquine is the usual choice for use in chloroquine-resistant areas, but it is ineffective in a few areas of high-level resistance, such as Thailand's borders with Cambodia and Myanmar (Burma).
Another issue concerning the use of drugs such as chloroquine, doxycycline and mefloquine is the need to continue taking these agents for four weeks after the traveler leaves areas where malaria is endemic, since these drugs are not active against the liver stage of the parasite. Patients with repeated short exposures to malaria-endemic areas often fail to comply with post-travel prophylaxis. Atovaquone-proguanil, which has recently become available in the United States as a combination pill, requires only a one-week postexposure continuation.
The article includes maps that highlight areas where malaria is endemic, maps that highlight zones of antimalarial drug resistance, and tables that recommend dosing regimens according to zones of resistance (see accompanying table), dosing information, and listings of possible side effects.
|Travel zone||Drug of choice*|
|No chloroquine resistance||Chloroquine, 150 mg (two tablets) once weekly|
|Chloroquine resistance||Mefloquine, 250 mg once weekly|
|Atovaquone-proguanil (20 mg/10 mg) once daily. Can stop medication one week after leaving area.|
|Chloroquine and mefloquine resistance||Doxycycline, 100 mg once daily|
Side effects of antimalarial agents are generally mild and include nausea, diarrhea, and headache. Some adverse events, such as occasional neuropsychiatric disturbances, can be serious. The authors note that general recommendations for travelers should be tailored to individual patients.
The authors also discuss the use of primaquine and other 8-aminoquinoline compounds that are being investigated for malarial prophylaxis in resistant areas. These agents, like atovaquone-proguanil, are active against the blood and liver stages of the parasite. In patients with long exposures in malaria-endemic areas, especially when infection with Plasmodium vivax is possible, primaquine is often used as “terminal prophylaxis” at the end of a standard prophylaxis regimen to ensure clearance of liver stores of parasites.