Quinine pharmacokinetics in young children with severe malaria

Children less than two years of age represent a substantial proportion of severe malaria cases in Africa. The standard treatment is parenteral quinine, but little is known about the pharmacokinetics and toxicity of quinine in this age group. We have studied the pharmacokinetics of quinine after intravenous (iv) and intramuscular (im) administration in a group of 20 children less than two years of age with severe malaria. A loading dose of 20 mg/kg of quinine dihydrochloride was followed by 10 mg/kg at 12-hr intervals. The im quinine was very rapidly absorbed, reaching high peak concentrations of 16.4 +/- 3.7 mg/L (mean +/- SD) in 1.1 +/- 0.4 hr. Mean peak levels after iv administration were also high (17.5 +/- 2.4 mg/L). Free quinine levels at 4 hr postadministration ranged from 0.27 to 1.89 mg/L (0.87 +/- 0.53 mg/L). At 2 hr and 4 hr after commencing treatment, an electrocardiogram showed a significant lengthening of the QRS interval compared with baseline (15.6 +/- 21.4%; P = 0.007 and 17.3 +/- 21.9%; P = 0.006 at 2 hr and 4 hr, respectively), whereas this was not observed in a control group of nine older children (age range = 24 months to 10 years) receiving the same im dosage regimen. Free and total quinine levels were not significantly correlated with changes in the QRS interval. Levels of alpha(1)-acid glycoprotein, which binds quinine within the circulation, did not differ between the younger and the older children. These findings raise the possibility that young children are more susceptible to quinine toxicity than older children, and indicate the need for further evaluation of quinine dosage regimens in this age group.