Tracking Resistance to Artemisinin (TRAC)

Because the artemisinins are the most potent antimalarial drugs, the reduction in parasite numbers is rapid. Therefore, early measures of reducing parasite counts are needed. This study will look at conventional markers of parasite reduction e.g. parasite clearance time, parasite reduction ratio, and the time to achieve a fall of 50%, 90% and 99% of the pre-treatment parasitaemia. Defining artemisinin resistance requires the use of artesunate (AS) alone because it is now appreciated that the partner drug in a combination treatment has a significant impact on the rate of parasite clearance. This study will dose patients for 3 days with AS alone (or longer until parasites clear) and measure the parasite count frequently in order to be able to define an accurate regression line of a graph of the natural logarithm of the parasite count (Y axis) versus time (X axis). This will be followed by a full course of an artemisinin combination therapy (ACT). Two different dose regimens of artesunate will be compared at all sites except those in western Cambodia, as unpublished observations from the Thai-Myanmar border suggest the standard lower daily dose of 2mg/kg may enable the earlier detection of low level resistance than a 4mg/kg daily dose.