Abstract: 　AIM: To explore the in vitro sensitivity of artesunate-sensitive and -resistant Plasmodium falciparum to chloroquine and amodiaquine and to observe the effect of artesunate combined with chloroquine and artesunate combined with amodiaquine on artesunate-resistant P.falciparum. METHODS: The sensitivity of the artesunate-sensitive and -resistant P.falciparum to chloroquine and amodiaquine and their combination with artesunate was compared by using Rieckmann′s in vitro micro-technique.RESULTS: The ID\-\{50\} and ID\-\{95\} values of chloroquine, amodiaquine and artesunete were 90.9, 50.9, 9.6 nmol/L and 320.0、320.0, 40.0 nmol/L to the artesunate-sensitive P.falciparum respectively and were 112.0, 133.5, 85.1 nmol/L and 320.0, 320.0, 400.0 nmol/L to artesunate-resistant P.falciparum, respectively. When artesunate was combined with chloroquine, the ID\-\{50\} values of the 2 drugs were 3.2 and 20.0 nmol/L to the artesunate-resistant P.falciparum. When artesunate was combined with amodiaquine, the ID\-\{95\} values of the 2 drugs were 3.2 and 5.0 nmol/L to the artesunate-resistant P.falciparum, respectively. CONCLUSION: The artesunate-resistant P.falciparum has no cross resistance to chloroquine and amodiaquine, however, artesunate combined with chloroquine or amodiaquine exhibit an apparent synergistic effect in vitro.\;

Key words: Plasmodium falciparum, artesunate, chloroquine, amodiaquine, combination of drugs, in vitro test