Studies of Methemoglobin Concentrations of Three Human Erythrocyte Genotypes (Hb AA, Hb AS, and Hb SS) in the Presence of Five Antimalarial Drugs

Malaria remains the world’s most devastating human parasitic infection. Our goal was to assess the capacity of increasing concentrations of five antimalarial drugs (FansidarTM, HalfanTM, Quinine, CoartemTM and Chloroquine phosphate) to elicit the generation of methemoglobin in three human erythrocyte genotypes (Hb AA, Hb AS and Hb SS). Spectrophotometric method was used for determination of plasma methaemoglobin concentration in the presence of 0.2 g%, 0.4 g%, 0.6 g% and 0.8 g% (w/v) of the five antimalarial drugs. The five antimalarial drugs showed a concentration dependent variability to cause the elevation of plasma methemoglobin concentration in the three genotypes. Specifically, CoartemTM, exhibited the highest propensity to elevate plasma methemoglobin concentration. However, the other four antimalarial drugs showed a statistically significant (P<0.05) but minimal effect to cause elevation of plasma methemoglobin concentration. For instance, with Hb AS blood sample and at drug concentration of 0.8g%, methaemoglobin concentrations (percentage) 0f 3.03±1.82, 2.65±0.45, 6.41±1.21, and 3.02±0.98 were obtained for halfan, quinine, coartem and chloroquine phosphate, respectively. The control value was 2.17±1.82% of methemoglobin. The oxidative potentials of these four antimalarial drugs and their metabolites in the red cells did not overwhelm the erythrocyte methemoglobin reducing capacity that could elicit the presentation in vitro toxic methemoglobinemia.