1 Twelve children with acute falciparum malaria were treated with 25 mg/kg chloroquine orally in three divided doses at 24 h intervals. 2 Concentrations of chloroquine and its metabolite, desethylchloroquine, were measured in plasma from the beginning of treatment for up to 7 days using a high pressure liquid chromatography (h.p.l.c.) technique. 3 Chloroquine was detectable in plasma within 30 min of giving the drug. Peak level was reached in 1-8 h after the first dose of 10 mg/kg and the peak concentrations ranged between 65 and 263 ng/ml. 4 Chloroquine concentration declined slowly in plasma after stopping drug administration so that the concentration at the seventh day was 37.5% of the concentration on the third day. The apparent half-life was 3-4 days. 5 Desethylchloroquine was detectable in plasma within 30 min of giving chloroquine and peak levels were reached in 2-12 h. Peak concentration after the first dose of chloroquine ranged between 9 and 62 ng/ml. 6 Desethylchloroquine was also slowly cleared from plasma and mean concentration at the end of 7 days was 49% of the mean concentration at the end of 3 days.

The single dose disposition of chloroquine was studied in five children with kwashiorkor and six normal control children after an oral dose of 10 mg kg‐1 of chloroquine base. Plasma concentrations of chloroquine and its main metabolite were assayed by high performance liquid chromatography (h.p.l.c.). Chloroquine was detectable for up to 21 days in all the subjects. Chloroquine was detectable in all the subjects within 30 min after giving the drug except in one subject. Peak levels were reached between 0.5 and 8 h in all the subjects (with no significant difference in the tmax between the two groups of children). Peak plasma chloroquine concentrations in the children with kwashiorkor varied from 9 ng ml‐1 to 95 ng ml‐1 (mean 40 +/‐ 34 ng ml‐1). Peak chloroquine concentrations in the controls varied between 69 ng ml‐1 and 330 ng ml‐1 (mean 134 +/‐ 99 ng ml‐1). The mean AUC in the kwashiorkor children was significantly lower than the mean AUC in the control children (P less than 0.001). Peak plasma desethylchloroquine concentrations in the children with kwashiorkor varied between 3 and 13 ng ml‐1 (mean 6 +/‐ 9 ng ml‐1) while in the controls the concentrations varied between 14 and 170 ng ml‐1 (mean 50 +/‐ 61 ng ml‐1). There was no significant difference in the half‐life of chloroquine between the kwashiorkor children and the normal control children. The possible influence of a different binding and distribution pattern of chloroquine in kwashiorkor could not be assessed in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

1 Ten children with Plasmodium falciparum malaria were treated with 25 mg/kg chloroquine over 3 days and observed for 7 days. 2 Chloroquine was determined in the red blood cells and plasma, and the red blood cell/plasma chloroquine concentration ratio was correlated with the disappearance of the parasites from the blood. It was found that this ratio decreased with the disappearance of the parasites and remained almost steady after the parasites had disappeared completely from the blood.3 The half-life (ty) and the elimination rate constant of the 'terminal' elimination slope (kg3) of the plasma log concentration-time curve were estimated to be 135.9 + 9.92 h and 0.005 0.001 h-' (s.d.) respectively.4 The t½, and X,3 calculated from the red blood cell log concentration-time curve were not significantly different from the corresponding values calculated from the plasma log concentrationtime curve.