Primaquine (15 mg/day for 14 days) plus chloroquine is more effective than chloroquine alone or primaquine (15 mg/day for 5 days) plus chloroquine in preventing relapses of vivax malaria. Primaquine (five days) plus chloroquine appears no better than chloroquine. Countries should follow the WHO's recommendation for 14-day primaquine plus chloroquine regimen. Alternative regimens need to be evaluated in randomized controlled trials, which should also consider variations in regional P. vivax strains and the possibility of primaquine resistance, reinfection, and adherence in those who relapse.
Radical curative efficacy of five-day regimen of primaquine for treatment of Plasmodium vivax malaria in India.
For over 4 decades the antimalarial program in India has been prescribing a 5-day primaquine regimen as an antirelapse therapy to treat Plasmodium vivax malaria. In view of conflicting reports on the effectiveness of this regimen in the Indian subcontinent, and the varying prevalence of P. vivax in various ecosystems in India, the antirelapse efficacy of this regimen was evaluated in Orissa, a malaria endemic state in eastern India where P. falciparum predominates. In 723 cases of P. vivax infection treated with chloroquine alone and followed up weekly for 1 yr, the prevalence of recurrence of parasitaemia with fever was 8.6%. Among another 759 P. vivax cases treated with chloroquine and a 5-day regimen of primaquine at 15 mg/day (adult dose), the recurrence of infection was 6.5%. The difference in recurrence was not significant (P = 0.53). It is important to note that in a great majority of cases of P. vivax in this area, infection did not recur even without treatment with primaquine. This finding, that the use of the 5-day primaquine regimen with chloroquine had no significant advantage over the use of chloroquine alone, undermines the rationale of using primaquine as an antirelapse drug in forested areas with a high prevalence of P. falciparum.