Flutamide-induced methemoglobinemia

The authors report a case of clinical methemoglobinemia occurring one year after a patient began receiving flutamide 750 mg/d for prostate cancer with bone metastasis. The patient presented with severe cyanosis involving his lips and proximal extremities and moderate dyspnea. Methemoglobinemia was 16.2 percent of the total hemoglobin and intravenous ascorbic acid was administered. Clinical examination and laboratory analysis revealed no other cause. There was no biochemical evidence of congenital methemoglobinemia and no other regular drug use or chemical exposure was found. Moreover, clinical improvement and normalization of the methemoglobin level after the drug was discontinued is highly suggestive of flutamide-induced methemoglobinemia. Due to its chemical structure derived from anilide, flutamide may be considered as a potential methemoglobin-inducing agent.