Primaquine relapse prevention

Non-falciparum malaria (like P. vivax) can still be treated with chloroquine although chloroquine resistant P. vivax has been reported from Irian Jaya and Papua New Guinea. In those areas treatment with mefloquine is recommended. To treat the liverstages an additional 2-3 weeks treatment with primaquine is given. It appears that tafenoquine (dosed once a week), a new 8-aminoquinoline, would be a better replacement for primaquine in preventing relapses in P. vivax malaria. 

Primaquine is used for treating and preventing late relapses of 3- and 4-day malaria as well as tropic malaria. Synonyms of this drug are avion and others. 

Primaquine is readily absorbed from the gastrointestinal tract, and in contrast to chloroquine, it is not bound extensively by tissues. It is rapidly metabolized, and the metabolites are reported to be as active as the parent drug itself. Peak plasma levels are reached in 4 to 6 hours after an oral dose, with almost total drug elimination occurring by 24 hours. The half-life is short, and daily administration is usually required for radical cure and prevention of relapses. 

Standard therapy for these infections includes chloroquine to eradicate erythrocytic forms and primaquine to eradicate liver hypnozoites and prevent a subsequent relapse. Chloroquine is given acutely, and therapy with primaquine is withheld until the G6PD status of the patient is known. If the G6PD level is normal, a 14-day course of primaquine is given. Prompt evaluation of the G6PD level is helpful, since primaquine appears to be most effective when instituted before completion of dosing with... 

Standard chemoprophylaxis does not prevent a relapse of vivax or ovale malaria, because the hypnozoite forms of these parasites are not eradicated by chloroquine or other available agents. To markedly diminish the likelihood of relapse, some authorities advocate the use of primaquine after the completion of travel to an endemic area. 

Clinical Use. Primaquine is typically used to treat the relapses of specific forms of malaria,12 and is generally administered in acute or severe exacerbations, or when other drugs (chloroquine, mefloquine) are ineffective in suppressing malarial attacks. Primaquine may also be used to prevent the onset of malaria in individuals who are especially at risk because of prolonged exposure to the disease.50 This drug is administered orally. 

Primaquine attacks plasmodia in the exoerythrocytic stages. It is effective for preventing relapse and as a prophylactic measure when staying in an infested area. Primaquine may cause hemolytic anemia, especially in patients who are deficient in glucose 6-phosphate dehydrogenase. 

Primaquine, an 8 aminoquinoline (26.3 mg daily for 14 days), is recommended only for the radical cure of vivax malaria, the prevention of relapse in vivax malaria, or following the termination of chloroquine phosphate suppressive therapy in an area where vivax malaria is endemic. 

Primaquine may disrupt the parasite s mitochondria and bind to native DNA. The resulting structural changes create a major disruption in the metabolic process. The gametocyte and exoerythrocyte forms are inhibited. Some gametocytes are destroyed, whereas others are rendered incapable of undergoing maturation division in the mosquito gut. By eliminating tissue (exoerythrocyte) infection, primaquine prevents development of blood (erythrocytic) forms responsible for relapses in vivax malaria. 

Primaquine, in contrast with other antimalarials, acts on tissue stages (exoerythrocytic) of plas-modia in the liver to prevent and cure relapsing malaria. The structure of primaquine is shown in... 

Pamaquine was synthesized in 1952, this 8-aminoquinoline was the first drug capable of preventing the relapses in Plasmodium vivax malaria. Toxicological concerns led to restrictions in the use of Pamaquine. Primaquine another 8-aminoquinoline derivative has been used since 1950 s for the eradication of liver stages in course of Plasmodium vivax infections. 

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