We do not know whether PQ added to treatment regimens for patients with P. falciparum infection reduces transmission of malaria. In individual patients, it reduces gametocyte prevalence and density. In practical terms, even if PQ results in large reductions in gametocytes in people being treated for malaria, there is no reliable evidence that this will reduce transmission in a malaria-endemic community, where many people are infected but have no symptoms and are unlikely to be treated. Since PQ is acting as a monotherapy against gametocytes, there is a risk of the parasite developing resistance to the drug. In terms of harms, there is insufficient evidence from trials to know whether the drug can be used safely in this way in populations where G6PD deficiency occurs.
In light of these doubts about safety, and lack of evidence of any benefit in reducing transmission, countries should question whether to continue to use PQ routinely in primary treatment of malaria. Further synthesis of observational data on safety and new trials may help elucidate a role for PQ in malaria elimination, or in situations where most infected individuals are symptomatic and receive treatment.
A prospective study evaluating the efficacy of a single, 45-mg dose of primaquine, as a gametocytocidal agent, in patients with Plasmodium falciparum malaria in Mumbai, India.
The efficacy of a single dose of 45 mg primaquine, as a gametocytocidal agent, was assessed in Mumbai, India, among adults with uncomplicated or severe Plasmodium falciparum malaria. All the patients investigated had been found gametocytaemic, with at least 56 gametocytes/microl blood, within the first 72 h of their illness. Those with uncomplicated malaria, like those with severe malaria, were randomized to receive or not receive primaquine. All the patients were followed up for 29 days post-admission, for gametocytaemia and gametocyte viability (as determined by exflagellation). Among those with uncomplicated malaria, six (27.3%) of the 22 who did not receive primaquine but only one (4.2%) of the 24 who did receive the drug, on day 4, remained gametocytaemic on day 29 (P < 0.05). Similarly, seven (31.8%) of the 22 severe cases who did not receive primaquine but only two (9.5%) of the 21 severe cases who received the drug, on day 8, were found gametocytaemic on day 15 (P < 0.05). While the single, 45-mg dose of primaquine recommended by the World Health Organization was effective in clearing gametocytes from the blood of > 90% of the present cases of malaria, > 4% of the patients with uncomplicated malaria and > 9% of those with the severe disease continued to harbour gametocytes in their peripheral blood 29 and 15 days after taking the primaquine, respectively.
                Copyright 2004 The Liverpool School of Tropical Medicine