In vivo efficacy of mefloquine for the treatment of Falciparum malaria in Brazil

J Infect Dis. 1999 Dec;180(6):2077-80. doi: 10.1086/315141.


Ninety-four patients with falciparum malaria were treated with mefloquine (1000-mg single dose) and remained hospitalized in a malaria-free area for a minimum of 28 days. There was 1 parasitologic failure (grade I resistance [RI]) for a 99% cure rate (95% confidence interval, 94.2%-99.7%). Mean parasite clearance time by thick smear was 45.7 h (SD, 11.4 h). The subject in whom therapy failed had a parasite clearance time (71 h) >2 SD above the population mean. His plasma mefloquine level 48 h after administration was lower (578 ng/mL) than the range of levels from 8 randomly selected cured subjects (834-2360 ng/mL). The IC50 to mefloquine for the recrudescent strain of the RI failure was in the upper 90th percentile of IC50 values from 30 cured subjects. These results show a high mefloquine cure rate but document the onset and mechanism of the emergence of resistance.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Antimalarials / pharmacology
  • Antimalarials / therapeutic use*
  • Brazil
  • Drug Resistance
  • Humans
  • Malaria, Falciparum / drug therapy*
  • Male
  • Mefloquine / pharmacology
  • Mefloquine / therapeutic use*
  • Middle Aged
  • Plasmodium falciparum / drug effects
  • Treatment Outcome


  • Antimalarials
  • Mefloquine