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 r ecommended as the drug of first choice for the treatment of Plasmodium viva x and P. falciparum infections, even though >50% of local isolates of P. fa lciparum 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 sup ervised primaquine (45 mg given on day 8) was investigated in 90 patients w ho had been treated with CQ. Of these, 15 were found to be CQ-sensitive pat ients, 61 were resistant (49, eight and four considered RI, RII and RIII, r espectively) 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)/mu l, respectively. Despite supervis ed 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 ther efore appears to be a need to review the current, gametocytocidal, primaqui ne-dosage schedule and to re-treat patients who remain gametocytaemic with higher doses of primaquine, as an important, transmission-blocking strategy .