Amodiaquine was compared to chloroquine in two groups of Filipino patients with uncomplicated falciparum malaria. Every patient received 25 mg/kg of base orally given over three days. In a hospital study, all eight patients receiving chloroquine cleared their parasitemia by day 6, but six of eight patients receiving amodiaquine failed to clear parasitemia and in four patients there was no response at all (RIII resistance); this difference was significant (P < 0.01). In a village based study, there was initial clearing of parasitemia in each patient. However, recrudescent infection occurred in all five patients receiving amodiaquine (RI resistance). Five of six falciparum infections were sensitive to chloroquine, while parasitemia reappeared in one patient. In this village, resistance to amodiaquine was significantly more common than resistance to chloroquine (P < 0.05).
To our knowledge, this is the first report of amodiaquine being substantially worse than chloroquine in the treatment of Plasmodium falciparum infection.