Abstract: 　Objective] To compare the sensitivity of artesunate sensitive and artesunate resistant P falciparum to pyronaridine,mefloquine and quinine and to understand the effect of artesunte combined with the above mentioned 3 drugs respectively on artesunate resistant P falciparum . [Methods] Rieckmanns in vitro miorotechnique was used. [Results] The ID 50 values of pyronaride,mefloquine, quinine and artesunate were 59 0, 69 7, 283 8 and 9 6 nmol/L to artesunate sensitive P falciparum ;the ID 50 of the 4 drugs mentioned above were 170 6, 63 2, 272 4 and 85 1 nmol/L to the artesunate resistant P falciparum , respectively. In artesunate pyronaridine combinaton, the ID 50 values were 1/3 7 (22 8/85 1) and 1/4 7 (36 6/170 6) of the 2 drugs singly used.In artesunate mefloquine combinaton,the ID 95 is 1/125 (3 2/400) and 1/16 (80/128) of the 2 drugs singly used, respectively. [Conclusion] The artesunate resistant P falciparum isolate has no cross resistance to mefloquine and quinine.When artesunate was used in combination with the 2 drugs mentioned above respectively,the efficacy proved to be enhanced.

Key words: P. falciparum, artesunate, pyronaridine, mefloquine, quinine, in vitro assay.