Feng LuQi GaoKesinee ChotivanichHui XiaJun CaoRachanee UdomsangpetchLiwang CuiJetsumon SattabongkotJiangsu Institute of Parasitic DiseasesMahidol UniversityBengbu Medical CollegePennsylvania State UniversityArmed Forces Research Institute of Medical Sciences, Thailand2018-05-032018-05-032011-08-01American Journal of Tropical Medicine and Hygiene. Vol.85, No.2 (2011), 197-201000296372-s2.0-80051543496https://repository.li.mahidol.ac.th/handle/20.500.14594/12019In the face of recent increase of Plasmodium vivax malaria in central China, we conducted a study to evaluate in vitro susceptibility of temperate-zone P. vivax parasites to antimalarial drugs. During 2005-2006, in vitro drug susceptibility was measured for 42 clinical P. vivax isolates by using a schizont maturation inhibition technique. Geometric means of 50% inhibitory concentrations (IC50s) and 95% confidence intervals (CIs) were 10.87 (4.50-26.26) ng/mL for chloroquine, 4.21 (1.88-9.42-8) ng/mL for mefloquine, 11.82 (6.20-22.56) ng/mL for quinine, 0.13 (0.09-0.20) ng/mL for artesunate, 18.32 (8.08-41.50) ng/mL for pyrimethamine, and 17.73 (10.29-30.57) ng/mL for piperaquine. The IC50for chloroquine was lower than those obtained from isolates from Thailand and South Korea, suggesting that chloroquine remained effective against P. vivax malaria in central China. The results further indicated that temperate-zone P. vivax isolates from China were more susceptible to chloroquine, quinine, and mefloquine than isolates from Thailand. Copyright © 2011 by The American Society of Tropical Medicine and Hygiene.Mahidol UniversityImmunology and MicrobiologyMedicineArticleSCOPUS10.4269/ajtmh.2011.10-0070