Antimalarial properties of imipramine and amitriptyline.

Dietary riboflavin deficiency is known to diminish malarial parasitemia. In this study, we determined whether imipramine and amitriptyline, drugs which inhibit riboflavin metabolism, have antimalarial efficacy. In addition, we evaluated whether these drugs, like other antimalarial agents, increase the hemolytic response to ferriprotoporphyrin IX (FP). The growth of Plasmodium falciparum (FCR3) in the absence and presence of these drugs (10 to 75 μM) was measured by determining (3H)hypoxanthine uptake by intraerythrocytic parasites for 48 h in RPMI 1640 medium. The uptake of (3H)hypoxanthine was significantly reduced in a dose-dependent manner by both imipramine and amitriptyline. The IC50 values of imipramine and amitriptyline at 48 h were 56 and 45 μM, respectively. Both drugs enhanced hemolysis induced by FP (10 or 20 μM). No hemolysis by these drugs was detected in the absence of FP. It is concluded that the tricyclic antidepressants, imipramine and amitriptyline, possess substantial antimalarial properties.