In terms of therapy, CQ and primaquine (PQ) are still the drugs of choice for the treatment of vivax malaria in many endemic areas, Brazil included. It is important however to keep in mind that side effects of these drugs could be erroneously taken as clinical severity associated to the parasite infection. In the case of CQ, it is considered a safe drug, despite the occurrence of pruritus, which most of the time is considered to be a minor effect and rarely requires the drug withdrawal [165] . Psychosis on the other hand is a more severe complication [75, 166] , as well as cardiac arrhythmia [29] . Atypical complications of its use such as severe gastric bleeding were associated with haemophilia A [50] . In the case of PQ, tranquillity is not the same as with CQ, because PQ is able to induce metahaemoglobinaemia [42, 51] and severe haemolysis [44] in patients with G6PD deficiency. The burden of the deficiency in Brazil is poorly measured but the few data available in endemic areas for malaria has shown it to be between 3.0% [149] and 5.8% [167] among men, since the deficiency is linked to the X-chromosome. In the case of Brazil, the prescription of PQ in the abbreviated regimen (0.5 mg/kg/day for 7 days) without any routine G6PD screening may contribute to increase the frequency and severity of the side effects triggered by this drug, as confirmed by the reports of patients with blackwater fever after PQ use, including one fatal case [63, 71, 91, 92, 168] . To complicate matters, for the radical cure, the new drug under late stage clinical investigation, tafenoquine, shows no evidence that it is safer than PQ in G6PD deficient [169] .