ACTIVITY OF PYRONARIDINE AND MEPACRINE AGAINST 12 STRAINS OF PLASMODIUM-FALCIPARUM IN-VITRO

Pyronaridine, an acridine derivative, has been found effective in Chin a for the treatment of drug-resistant falciparum malaria. The activiti es of pyronaridine and mepacrine were compared with those of standard antimalarial drugs in vitro against chloroquine-sensitive (CS) and chl oroquine-resistant (CR) Plasmodium falciparum isolates to investigate cross resistance. The 50% inhibitory concentrations (IC50) against the resistant isolates were 2.8-fold higher than the sensitive isolates f or pyronaridine (CS=7.3 nM; CR=20.5 nM) and 3.2-fold higher for mepacr ine (CS=13.3 nM; CR=42.6 nM). These same isolates showed an Ii-fold di fference in sensitivity to chloroquine with mean IC50 values of 21 nM for sensitive and 239 nM for resistant parasites. A significant correl ation was observed between parasite sensitivity (IC50) to pyronaridine and the drugs, mepacrine, amodiaquine and chloroquine. However, the h igh level of activity seen with pyronaridine, even against the CR isol ates, should encourage further field trials with this drug.