Efficacy of drug prophylaxis.

Area of Science:

• Medical Entomology
• Tropical Medicine
• Pharmacology

Background:

• Chloroquine-resistant Plasmodium falciparum has complicated malaria control, especially for non-immune international travelers.
• Previous shifts to newer antimalarials like amodiaquine were based on efficacy in endemic areas, but serious adverse reactions have been reported.
• Concerns over drug toxicity and resistance necessitate careful selection of malaria prophylaxis.

Purpose of the Study:

• To evaluate the challenges in selecting appropriate malaria chemoprophylaxis for non-immune travelers.
• To assess the limitations of using field data from partially immune populations to predict drug efficacy in non-immune individuals.
• To highlight the difficulties in defining 'adequate protection' against malaria due to focal resistance patterns.

Main Methods:

• Review of international studies and clinical case reports on antimalarial drug efficacy and adverse events.
• Analysis of malaria prevention guidelines and recommendations for international travelers.
• Examination of the discrepancies between drug resistance data in endemic populations and expected efficacy in non-immune travelers.

Main Results:

• Breakthrough malaria infections occurred in travelers taking chloroquine prophylaxis in East Africa.
• Serious adverse reactions have been documented with pyrimethamine/dapsone, pyrimethamine/sulphadoxine, and amodiaquine.
• Field data on drug resistance in indigenous communities are not directly applicable to non-immune travelers due to varying immunity and resistance levels.

Conclusions:

• Defining 'adequate protection' for malaria chemoprophylaxis in non-immune travelers remains a significant challenge.
• Focal and variable patterns of Plasmodium falciparum resistance limit the ability to map resistance comprehensively.
• Specialists must balance the safety and efficacy of antimalarial drugs, considering the limitations of current data for non-immune populations.