Azithromycin: Antimalarial Profile against Blood- and Sporozoite-Induced Infections in Mice and Monkeys

Abstract

Puri, S. K. and Singh, N. 2000. Azithromycin: Antimalarial Profile against Blood- and Sporozoite-Induced Infections in Mice and Monkeys. Experimental Parasitology94, 8–14. The spectrum of antimalarial activity of the new macrolide antibiotic azithromycin was evaluated against blood- and sporozoite-induced infections with a chloroquine-resistant strain of Plasmodium yoelii nigeriensis (N-67) in Swiss mice and with simian parasite Plasmodium cynomolgi B in rhesus monkeys. Against experimental rodent malaria, a 70 mg/kg/day dose showed curative blood-schizontocidal activity in a four-dose regimen administered orally from day 0 to day 3 or from day 2 to day 5 to mice harboring established infection. The curative response was also obtained with a 40 mg/kg/day dose administered in an extended seven-dose (days 0–6) regimen. Azithromycin was also effective in the causal prophylactic test, since a 50 mg/kg dose from day −1 to day +2 protected mice against P. y. nigeriensis (N-67) sporozoite challenge. In comparison, erythromycin did not show either of the above activities up to a 405 mg/kg/day dose in identical regimens. Comparison of the ED90 values showed that azithromycin was 31-fold more effective than erythromycin as a blood schizontocide. In the simian model, trophozoite-induced infections of P. cynomolgi B were cured with 25 mg/kg/day azithromycin administered for 7 days. In the causal prophylactic test, the prepatent period was significantly extended in monkeys challenged with P. cynomolgi B sporozoites, presumably because of the growth inhibition of preerythrocytic schizonts in hepatocytes. Azithromycin did not exhibit any hypnozoitocidal (dormant exoerythrocytic stages) activity at 25 mg/kg/day in a seven-dose regimen.