CHLOROQUINE BIOASSAY USING MALARIA MICROCULTURES

The in vitro microculture technique was used to develop a relatively s imple bioassay for estimating chloroquine (CQ) in plasma or serum. Chl oroquine concentrations were determined by multiplying the maximum inh ibitory dilution of plasma/serum required to inhibit growth of the CQ- sensitive FC27 isolate of Plasmodium falciparum by the minimum inhibit ory concentration of CQ against the same isolate. Human serum samples spiked with CQ gave similar measurements using both bioassay and high- performance liquid chromatography. The antimalarial activity of plasma or serum samples collected from 13 patients treated with CQ was equiv alent to the sum of the combined activity of CQ and its metabolite, mo no-desethylchloroquine. The concentration of these components using th e bioassay could be expressed conveniently in terms of CQ concentratio n equivalents. This bioassay can be used to estimate drug concentratio ns without the use of sophisticated methods or equipment. Since it is based on the microculture technique, it can be easily carried out in c onjunction with the drug susceptibility test to assess CQ treatment fa ilures in malaria patients.