PROLONGED EXPOSURE OF PLASMODIUM-FALCIPARUM TO CIPROFLOXACIN INCREASES ANTIMALARIAL ACTIVITY

The minimum inhibitory concentration (MIC) of ciprofloxacin was determ ined for 2 isolates of Plasmodium falciparum at 48, 96, and 144 hr. Th e MIC decreased from mean values of28.1 mu g/ml for the FC isolate and 27.2 mu/ml for the K1 isolate at 48 hr to 2.8 mu g/ml and 4.4 mu g/ml , respectively, at 96 hr. Concentrations of 0.1-1.0 mu g/ml were effec tive in suppressing parasite growth over 144 hr of incubation. These f indings indicate that the multiplication of malaria parasites can be i nhibited by clinically achievable concentrations of ciprofloxacin prov ided that exposure to the drug is prolonged over several asexual eryth rocytic cycles. They also raise the possibility that this antibiotic c ould be used eventually, in combination with a rapidly acting but nonc urative drug regimen, to treat patients with refractory falciparum inf ections.