An antiprotozoal agent inhibits complex III activity on dihydroorotate in isolated P. falciparum and P. yoelii mitochondria more potently than in rat liver mitochondria (EC50s 0.95 0.94 and 510 nM respectively) depolarizes the mitochondrial membrane in P. yoelii-infected mouse erythrocytes (EC50 260 nM) inhibits human BCRP- and P-glycoprotein-mediated transport in membrane vesicles (IC50s 0.23 and 6.8 M respectively) inhibits the growth of T. gondii in MRC-5 human lung fibroblasts in vitro (IC50 ~64 nM) increases mean survival of T. gondii-infected mice from 5.5 to 21.2 days (100 mg/kg per day)