Pharmacokinetic study of mefloquine in Thai children aged 5-12 years suffering from uncomplicated falciparum malaria treated with MSP or MSP plus primaquine.

A triple combination of mefloquine, sulfadoxine and pyrimethamine (MSP) was used with primaquine for the radical treatment of falciparum malaria in Thailand. Primaquine was reported to inhibit hepatic microsomal enzymes and drug metabolism in animal and man. 23 children hospitalized in the Hospital for Tropical Diseases, Faculty of Tropical Medicine, Bangkok, Thailand, were randomly allocated into two groups, group I received MSP equivalent to 20 mg base of mefloquine/kg body weight and group II received MSP plus primaquine (0.75 mg/kg). No statistical difference was noted for clinical response except the gametocyte clearance time was shorter in children given MSP plus primaquine (7 +/- 2.7 days) than the children given MSP alone (21.9 +/- 4.4 days) (P < 0.01). No serious side effects were recorded in this study. The plasma samples were obtained for kinetic calculations by HPLC in 18 children (11 in group I, 7 in group II). Mean Cmax was 7.4 +/- 5.2 h in group I and 6.6 +/- 7.0 h in group II. Mean t1/2, Cl/f and Vd/f were 9.8 +/- 1.6 days, 0.43 +/- 0.16 ml/min/kg and 8.84 +/- 4.21 l/kg in group I, 9.3 +/- 1.4 days, 0.41 +/- 0.12 ml/min/kg and 8.91 +/- 3.00 l/kg group II, respectively. The comparison of kinetic parameters in groups I and II revealed no significant difference (P > 0.05) suggesting no drug interaction. These kinetic values in children given MSP suspension were considerably different to those in adult patients with shorter tmax, t1/2 and MRT. The coadministration of MSP and primaquine in children would benefit by reducing the transmission of malaria in endemic areas.