G6PD and methemoglobinemia: However, PQ has several side effects [3], including (i) abdominal discomfort at doses greater than 0.5 mg/kg, (ii) oxidative hemolysis, which is most vulnerable in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, and is characterized by intravascular hemolysis, anemia, and hemoglobulinuric renal failure, and (iii) methemoglobinemia, especially in NADH-methemoglobin reductase deficient patients [4,5].