CLINICAL-RESPONSE AND SUSCEPTIBILITY IN-VITRO OF PLASMODIUM-VIVAX TO THE STANDARD REGIMEN OF CHLOROQUINE IN THAILAND

The clinical effectiveness of the standard regimen of chloroquine (CQ) (a total dose of 1500 mg, given over 48 h at 0, 6, 24 and 48 h) for t he treatment of Plasmodium vivax malaria in Thailand was investigated in 57 patients in an endemic area of Thailand (Chantaburi Province, ea stern Thailand). For radical treatment, an additional course of a tiss ue schizontocidal agent, primaquine, was given following the complete course of CQ. With this regimen, satisfactory whole blood concentratio n-time profiles of CQ and its major metabolite desethylchloroquine (DE CQ) were achieved. Mean whole blood levels of CQ and DECQ always much exceeded the reported therapeutic level of CQ (90 ng/mL) during the fi rst 7 d of treatment. All patients responded well, to the treatment; i n most cases, complete and rapid clearance of parasitaemia was observe d within the first 48 h. No reappearance of the parasitaemia was detec ted in peripheral blood films of any patient within 14 d of the evalua tion period. In 6 patients, however, reappearance of P. vivax parasita emia was observed after 30 d; 2 of them had not completed the course o f primaquine. There was no difference in whole blood concentrations of CQ and DECQ, admission parasitaemia, susceptibility of the isolates t o chloroquine in vitro, and parasite clearance time between patients w ith or without reappearance of parasitaemia. A prominent trend of dete riorating sensitivity of the parasite to the drug was, however, sugges ted.