Poor gametocytocidal activity of 45 mg primaquine in chloroquine-treated patients with acute, uncomplicated, Plasmodium falciparum malaria in Mumbai (Bombay): an issue of public-health importance

In the city of Mumbai (formerly Bombay), chloroquine (CQ) continues to be recommended as the drug of first choice for the treatment of Plasmodium vivax and P. falciparum infections, even though > 50% of local isolates of P. falciparum are resistant to it. Primaquine, an 8-aminoquinoline is also given to patients with falciparum malaria, in a single, 45-mg dose, to kill the gametocytes and so reduce transmission. The gametocytocidal activity of supervised primaquine (45 mg given on day 8) was investigated in 90 patients who had been treated with CQ. Of these, 15 were found to be CQ-sensitive patients, 61 were resistant (49, eight and four considered RI, RII and RIII, respectively) and 14 were lost before completion of the follow-up. The mean (S.D.) baseline gametocytaemias in the CQ-sensitive and RI-resistant cases were 665.1 (411.3) and 1537.4 (1045.5)/microliter, respectively. Despite supervised primaquine treatment, four of the 15 CQ-sensitive patients and 32 of the 49 patients found to be RI-resistant had gametocytes on day 29. There therefore appears to be a need to review the current, gametocytocidal, primaquine-dosage schedule and to re-treat patients who remain gametocytaemic with higher doses of primaquine, as an important, transmission-blocking strategy.