Aims: In Korea, chloroquine, in combination with primaquine, is the drug of choice for vivax malaria treatment. However, two cases of chloroquine-resistant P.vivax malaria have been reported in Korea. Since re-emergence in 1993, vivax malaria has been prevailing consistently and its selection pressure has been increasing. Furthermore, it is suggested that the parasite clearance time (PCT) increased annually. The aim of this study was to assess the trend of chloroquine susceptibility in Korean vivax malaria.
Methods: We retrospectively reviewed the medical records of the patients age more than 18 years old who had been diagnosed as Korean vivax malaria from five general hospitals in located in endemic area between January 2000 and December 2016. Treatment consisted of hydroxychloroquine (2000 mg base administered over 3 days) plus primaquine (15 mg base/daily for 14 days). PCT and fever clearance time (FCT) were measured to reveal the therapeutic efficacy of chloroquine.
Results: A total of 1366 malaria cases with vivax malaria were included. When the study periods were classified into three groups (2000-2006 years, 2006-2010 years, and 2011-2016 years), the range of median PCT (64hrs(IQR:50-83), 67hrs(IQR:58-78) and 74hrs(IQR:50-95), p=0.003) prolonged and the ratio of parasite clearance (47/150(68.7%), 65/177(65.3%) and 44/87(49.2%), p=0.005) decreased. The range of FCT (28hrs(IQR:15-43), 43hrs(IQR:29-76), and 48hrs(IQR:29-88), p<0.001) were extended over time. It was observed that mean total administered dose of chloroquine per body weight was reduced as time passed (23.4±5.1, 22.9±4.4, and 22.4±4.7, p=0.004).
Conclusions: The results presented here suggest that the trend of chloroquine susceptibility in Korea has continued to decline. The total administered dose of chloroquine based on treatment guideline was less than the WHO recommended total dose (chloroquine base 25mg/kg), which may have affected chloroquine efficacy over the study period. Administration of chloroquine depending on patients body weight and continuous monitoring of chloroquine susceptibility is needed.