Drugs that cure malaria caused by P. falciparum infection do not necessarily directly affect the gametocyte, which is the stage of the parasite that infects mosquitoes to complete the transmission cycle. Primaquine (PQ), a drug with antimalarial properties, does not cure P. falciparum infection but does kill P. falciparum gametocytes. Because of this property, this drug has long been recommended as a single dose or short course add-on to P. falciparum infection treatment regimens. It is now recommended by the World Health Organization (WHO) and several national malaria control programs, with the intention of reducing community level malaria transmission. However, this drug also has potentially serious side effects in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency, a common genetic variant. When they take this drug it may cause haemolysis (disintegration of red blood cells) which can be serious. This review examines the evidence of benefits and harms of PQ from trials where it has been used as an additional treatment intended to prevent malaria transmission.
We found no studies testing whether the drug influences transmission intensity of malaria, and just one small study suggesting it reduces the infectiousness of the parasite present in infected people to the mosquito. PQ probably reduces the potential infectiousness of the parasite in people, as measured by the numbers of gametocytes circulating in the blood for up to six weeks after treatment. Regarding safety, one study reported that there was a greater reduction in haemoglobin values in the PQ group at day 8, so the safety of the drug remains uncertain if given to populations where G6PD occurs. Evidence of benefit and of safety is insufficient to recommend routine use of PQ as an add-on for people being treated for malaria.
Graves, P.M.; Gelband, H.; Garner, P. Primaquine for reducing Plasmodium falciparum transmission. Cochrane Database of Systematic Reviews (2012) : [DOI: 10.1002/14651858.CD008152.pub2]