We have recently completed a series of cross-over clinical and pharmacokinetic evaluations of chloroquine, piperaquine, pyronaridine and primaquine in healthy subjects. These studied were approved by the ethical committee of FTM. All drugs were well tolerated with no clinically significant ECG changes. Four subjects were in two studies. This offers a unique opportunity to compare the electrocardiographic effects of chloroquine and piperaquine in the same subjects and therefore characterize the concentration-effect relationships, and thus relative safety.