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Primaquine is a medication used to treat and prevent malaria and to treat Pneumocystis pneumonia. It is taken by mouth. Primaquine should not be given to people with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to the risk of red blood cell breakdown. It may be used while breastfeeding if the baby is known not to have G6PD deficiency. It is available as a generic medication.
Medical uses
Malaria
Primaquine is primarily used to prevent relapse of malaria due to Plasmodium vivax and Plasmodium ovale. It eliminates hypnozoites, the dormant liver form of the parasite, after the organisms have been cleared from the bloodstream. Clarity in this regard is expected to be forthcoming soon. Use of primaquine in combination with quinine or chloroquine each of which is very effective at clearing P. vivax from blood, improves outcomes; they appear to also potentiate the action of primaquine.
As of 2016, the US Centers for Disease Control and Prevention recommends the use of primaquine for primary prophylaxis prior to travel to areas with a high incidence of P. vivax, and for terminal prophylaxis (anti-relapse therapy) after travel.
Pneumocystis pneumonia
Primaquine is also used in the treatment of Pneumocystis pneumonia (PCP), a fungal infection commonly occurring in people with AIDS and, more rarely, in those taking immunosuppressive drugs. To treat PCP effectively, it is usually combined with clindamycin.
Primaquine should not be administered to anyone with G6PD deficiency because a severe reaction can occur, resulting in hemolytic anemia.
Adverse reactions
Common side effects of primaquine administration include nausea, vomiting, and stomach cramps.
Pharmacology
Mechanism of action
Primaquine is lethal to P. vivax and P. ovale in the liver stage, and also to P. vivax in the blood stage through its ability to do oxidative damage to the cell. However, the exact mechanism of action is not fully understood.
Pharmacokinetics
Primaquine is well-absorbed in the gut and extensively distributed in the body without accumulating in red blood cells. Administration of primaquine with food or grapefruit juice increases its oral bioavailibity. In blood, about 20% of circulating primaquine is protein-bound, with preferential binding to the acute phase protein orosomucoid. With a half-life on the order of 6 hours, it is quickly metabolized by liver enzymes to carboxyprimaquine, which does not have anti-malarial activity. Renal excretion of the parent drug is less than 4%.
Chemistry
Primaquine is an analog of pamaquine which was the first drug of the 8-aminoquinoline class; tafenoquine is another such drug.
Society and culture
It is on the World Health Organization's List of Essential Medicines.
- SN-13272
Research
Primaquine has been studied in animal models of Chagas disease and was about four times as effective as the standard of care, nifurtimox.