Plasma concentrations and toxicity of chloroquine after slow intravenous infusion in patients with falciparum malaria

Five male patients with acute Plasmodium falciparum or Plasmodium vivax infections were infused with chloroquine diphosphate (15 mg kg-1) over four hours. Further does of chloroquine diphosphate (5 mg kg-1) were given at 12, 24, 36 and 60 hours. Plasma chloroquine concentrations were determined before and four hours after each dose and then daily until discharge. No serious cardiovascular toxicity was observed, and plasma chloroquine concentrations exceeding the putative minimum inhibitory concentration (MIC) of sensitive P. falciparum strains were reached within four hours of starting treatment. Further doses produced plasma concentrations which were sustained above the putative MIC, but showed no rapid increase into the range associated with toxicity.