Changes in Plasmodium falciparum gametocytaemia in children with chloroquine-sensitive asexual infections.

A non-compartmental pharmacokinetic model was used to describe the changes in gametocytaemia in nine children with chloroquine-sensitive Plasmodium falciparum malaria in whom asexual parasitaemia cleared within 72 h of chloroquine treatment. Peak gametocytaemia was 74 +/- 19.9 (se), range 24-198, geometric mean 58 sf (sexual forms)/microliter. Time to peak gamelocytaemia was 43.2 +/- 14.4, range 0-120 h. Following peak gametocytaemia, gametocytes persisted in blood for a period of 168-504 h. The decline from peak gametocytaemia was exponential with a half-life of gametocytaemia of 43.2 +/- 20.4, range 13.1-206 h. The mean pre-treatment sex ratio was male-biased and remained so till complete elimination of gametocytaemia. Peak microgametocytaemia, area under the curve of microgametocytaemia versus time, and the half-life of microgametocytaemia were significantly higher than those of macrogametocytaemia. The volume of blood completely cleared of macrogametocytaemia per unit time was significantly higher than that of microgametocytaemia. Macrogometocytes are cleared from the circulation faster than microgametocytes but chloroquine treatment of chloroquine-sensitive infections has little or no significant effect on gametocyte sex ratios in this group of children.