Volume 61, Issue 1
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


Resistance to antimalarial chemotherapy is one of the greatest difficulties for the control of malaria transmission. Seventy patients with Plasmodium falciparum malaria were included in a study of resistance to chloroquine and sulfadoxine-pyrimethamine therapy. Resistance levels RI, RII, and RIII were established. Eighteen infections (51%) cleared after chloroquine treatment and did not recur within 28 days of follow-up; these were classified as sensitive. Ten infections (29%) were resistant at the RI level. Resistance at level RII was observed in 5 (14%) cases, and RIII resistance was demonstrated in 2 infections (6%). With sulfadoxine-pyrimethamine, 28 (80%) infections were classified as sensitive. Six infections (17%) showed resistance at level RII, and 1 (3%) infection was resistant at the RI level. Resistance at level RIII was not observed. In a microtest for chloroquine and sulfadoxine-pyrimethamine sensitivity in vitro, schizont development was accomplished successfully in 70 blood samples. In vitro resistance to chloroquine was demonstrated in 15 of 70 (21%) of all isolates. Eight of 70 (11%) of all isolates showed resistance to sulfadoxine-pyrimethamine. Diversity of response of P. falciparum to the studied antimalarial drugs in the Guayana area of Venezuela is considered a problem restricting the control of malaria in this geographical area. A constant evaluation program monitoring P. falciparum drug sensitivity is necessary for preserving the efficacy of the established treatment.


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