Chloroquine 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 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. 

Chloroquine is a 4-aminoquinoline antimalarial agent used for the suppression and clinical cure of malaria. It is an excellent erythrocytic schizontocide. It does not prevent relapse in P. vivax and P. ovale malaria. It has no effect on pre and exoerythrocytic phase of the parasite. It also... 

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. 

The total dose of chloroquine base over 3 days should be approximately 25 mg/kg base. This is sufficient for Plasmodium malariae infection but, for Plasmodium vivax and Plasmodium ovale eradication of the hepatic parasites is necessary to prevent relapse, by giving ... 

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. 

THERAPEUTIC USES Chloroquine is inexpensive and safe, but its usefulness has dechned in those parts of the world where strains of P. falciparum are resistant. Except in areas where resistant strains of P. vivax are reported (Table 39-2), chloroquine is very effective in prophylaxis or treatment of acute attacks of malaria caused by P. vivax, P. ovale, and P. malariae. Chloroquine has no activity against primary or latent liver stages of the parasite. To prevent relapses in P. vivax and... 

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