Cytotoxicity assays of artemiside (Amd) combinations with the standard antimalarial drugs chloroquine (Ch), mefloquine (Mef), and piperaquine (P). The numbers represent the experimental results. The numbers in parentheses are the theoretical additive values, e.g., Amd2 (30.0 ng/ml), Ch2 (33.3 ng/ml), and their combination inhibit 13, 22, and 27% of untreated THP-1 growth, respectively. The theoretical additive value is 35% (13% ± 22%).