Concentrations of chloroquine and malaria parasites in blood in Nigerian children

Consumption of chloroquine (CQ) and subtherapeutic drug levels in blood are considered to be widespread in areas where malaria is endemic. A cross-sec tional study was performed with 405 Nigerian children to assess factors ass ociated with the presence of CQ in blood and to examine correlations of dru g levels with malaria parasite species and densities. Infections with Plasm odium species and parasite densities were determined by microscopy and PCR assays, Whole-blood CQ concentrations were measured by high-performance liq uid chromatography, Plasmodium falciparum, P, malariae, and P, ovale were o bserved in 80, 16, and 9% of the children, respectively, and CQ was detecte d in 52% of the children. CQ concentrations were >17 and < 100 nmol/liter i n 25% of the children, 100 to 499 nmol/liter in 14% of the children, and gr eater than or equal to 500 nmol/liter in 13% of the children. Young age, at tendance at health posts, and absence of parasitemia, were factors independ ently associated with CQ in blood. With increasing concentrations of CQ, th e prevalence of P. falciparum infection and parasite densities decreased. H owever, at concentrations corresponding to those usually attained during re gular prophylaxis (greater than or equal to 500 nmol/liter), 62% of childre n were still harboring P. falciparum parasites. In contrast, no infection w ith P, malariae and only one infection with P, ovale were observed in child ren with CQ concentrations of greater than or equal to 100 nmol/liter, Thes e data show the high prevalence of subcurative CQ concentrations in Nigeria n children and confirm the considerable degree of CQ resistance in that cou ntry, Subtherapeutic drug levels are likely to further promote CQ resistanc e and may impair the development and maintenance of premunition in areas wh ere malaria is endemic.