In vivo sensitivity monitoring of chloroquine for the treatment of uncomplicated vivax malaria in four bordered provinces of Thailand during 2009–2010

Abstract

Background & objectives: Chloroquine (CQ), followed by 14-day primaquine, is the recommended regimen forthe treatment of Plasmodium vivax infection in Thailand. CQ resistant P. vivax (CRPv) has not yet challengedthe efficacy of the drug. The present study was conducted to assess the current response of P. vivax to CQ alonein Thailand.Methods: A 28-day in vivo therapeutic efficacy study was conducted from June 2009 to December 2010 in 4sentinel sites. Recurrence of parasitaemia and the clinical condition of patients were assessed on each visitduring follow-up. The drug levels in recurrent patients’ blood were measured using HPLC. Data were analyzedusing the WHO 2008 program for the analysis of in vivo tests.Results: Of the total 212 patients included in the study, 201 completed the 28-days follow-up, while 11 wereexcluded. In five patients (2.5%), parasitaemia reappeared within the 28-days follow-up. On the day of recurrentparasitaemia, the level of chloroquine/desethylchloroquine (CQ-DCQ) was above the minimum effectiveconcentration (>100 ng/ml) in one patient, but lower in four patients.Conclusion: Reappearance of the parasite within 28 days of follow-up in one of five patients was due to parasiteresistance to CQ. The 2.5% prevalence of CQ treatment failure for P. vivax malaria in the study areas signals theneed to launch monitoring activities for CQ resistant P. vivax in malaria endemic areas in order to detect furtherdevelopment of parasite resistance and to estimate the level of burden across the country

Keywords

• Chloroquine resistance
• malaria
• parasitaemia
• P. vivax
• Thailan