We examined the plasmatic concentrations of quinine in patients with uncomplicated falciparum malaria in an endemic area of the Amazon region in Brazil in a prospective clinical trial, in which a standard three-day course of oral quinine plus doxycycline was used. We measured the quinine in the plasma samples on days 0 and 3by high performance liquid chromatography. The mean concentration of quinine was 6.04 ±2.21 μ μ μ μ μg/mL in male patients and 5.98 ±1.95 μ μ μ μ μg/mL in female patients. No significant differences in quinine concentration were observed between these two groups. All samples collected before starting treatment were negative for quinine. This information could help in the development of strategies for the rational use of antimalarial drugs in Brazil.

In the present study, we observed no effect of patient age on the steady-state concentrations of mefloquine in the plasma and erythrocytes. We found that the mefloquine concentration in the erythrocytes was approximately 2.8-times higher than in the plasma. There were no significant correlations between mefloquine concentrations in the erythrocytes and plasma for either age group.

SUMMARYWe determined the relationship between plasma and red blood cell concentrations of quinine in children with uncomplicated falciparum malaria from an endemic area of Amazonian region. Quinine was determined by high performance liquid chromatography with ultraviolet detection. In the steady state the ratio between plasma and red blood cell quinine concentration was 1.89 ± 1.25 ranging from 1.05 to 2.34. This result demonstrated that quinine do not concentrate in red blood cell of Brazilian children and characterize the absence of interracial difference in this relationship. KEYWORDS:Quinine; Quinine levels; Malaria, Chromatography.In the last decade there has been an effort at monitoring the blood levels of antimalarials in patients with falciparum malaria, an important tool in the evaluation of efficacy and effectiveness of antimalarial drugs 4,5 . The response of the developing malaria parasite to antimalarials is largely determined by the concentration of drug accessible to the parasite within the red cell and its sensitivity to that drug 4 . The level of antimalarial drug in the plasma is proportional to the concentration within the parasitized red cell and it is determined by several independent variables as the drug formulation, age, race, immunity, the fraction of drug absorbed, the apparent volume of distribution and the clearance 5,6,7 .There is a lack of knowledge about the relationship between plasma and red blood cell concentrations of quinine in Brazilian children with uncomplicated falciparum malaria in which the standard treatment with oral quinine was used 1 . This is essential for the success of the treatment once a marked interpersonal and interracial difference in quinine disposition have been demonstrated 3,4,5 . Therefore, this work was done to elucidate this relationship in an endemic area of Amazon region, in a prospective clinical treatment trial.This study was conducted from January 2006 to January 2007, with 10 male children with signs and symptoms of uncomplicated P. falciparum malaria. Their characteristics were as follows (means ± SDs): age, 9.2 ± 3.1 years (age range; five to 13 years); body weight, 21.2 ± 4.1 Kg, erythrocyte count, 3.21 ± 0.52 x 10 6 /µL; white blood count, 11,300 ± 4700/µL. The median initial parasitemia was 2100/µL (range; 900 to 4500/µL). The patients were admitted to the public Hospital of Cachoeira do Piriá, Brazil. Informed consent was obtained from their parents. Children with severe or mixed malaria were excluded. Patients who had taken any antimalarial drugs within the previous 48 hours were also excluded. This study was approved by the ethics committee of the Tropical Medicine Center of Para Federal University.After clinical assessment and confirmation by microscopic examination of blood smears, all patients were treated with 3-day oral treatment regimen of quinine base (487.5 mg), followed by doxycycline hydrochloride for five days and primaquine phosphate in the last day. Reappearance of infection was assessed for at least 28 days, by clinical eval...