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Primaquine phosphate has been used to prevent relapse as a radical cure after the acute-phase treatment of vivax and ovale malaria however. Many vivax malaria relapses have been reported following a standard dose of primaquine (15 mg/day for 14 days). A higher dose of primaquine (30 mg/day for 14 days) decreases the relapse rate, and the concomitant risk of gastrointestinal side effects tends to disappear when the drug is administered with food. G6PD deficiency is rare in the Japanese population. Although the relapsed phenomenon is reported globally, the higher dose of primaquine is currently recommended in Japan only for those returning from Southeast Asia or Papua New Guinea. Cases of 18 Japanese, including 13 vivax malaria and 5 ovale malaria, prescribed primaquine at a referral center in Japan, were analyzed retrospectively from 2007-2011. Data on diagnosis, treatment, and outcome were extracted from medical records. Of the 18, 10 with vivax malaria were administered the higher dose of primaquine. We found that only one suffered relapse-a vivax malarial case returning from Brazil and treated with the standard dose of primaquine. No ovale malarial case suffered relapse. None, including the 10 prescribed the higher primaquine dose, experienced any adverse side effects. Based on our findings, we recommend a higher dose of primaquine be used to prevent relapse when treating Japanese suffering from vivax malaria.

Since the discovery of glucose-6-phosphate dehydrogenase (G6PD) deficiency and pyruvate kinase deficiency, erythroenzymopathies associated with hereditary hemolytic anemia have been extensively investigated. Kinetic and electrophoretic studies have shown that most erythroenzymopathies are caused by the production of a mutant enzyme. Single amino acid substitutions have been determined in G6PD and phosphoglycerate kinase variants by studies of the enzyme. Except for these two enzymes, it has been difficult to purify and to characterize the patient's enzyme because of the low protein contents in red blood cells. Recent advance in recombinant DNA technology has made possible the isolation of normal genomic DNA or cDNA for several enzymes. These results permit us to study the molecular basis of erythroenzymopathies at the nucleotide level. Single base substitutions have been identified in aldolase, triosephosphate isomerase, G6PD and adenylate kinase variants by the cloning and nucleotide sequence of the patients' genes. To date, all of the enzyme-deficient variants which have been investigated are caused by point mutations. An exception is a hemolytic anemia secondary to increased adenosine deaminase (ADA) activity. Red cell ADA activity increases on the order of a hundred-fold in affected individuals. The basic abnormality appears to result from overproduction of structurally normal enzyme due to abnormal translational efficiency.