Krong Siem Reap

This research aims to find the best single dose of tafenoquine to treat Plasmodium vivax malaria in Southeast Asia. Tafenoquine is a recently approved alternative to the 14-day primaquine treatment for the dormant liver stage of this malaria type. Previous studies showed the standard 300 mg tafenoquine dose was less effective in Southeast Asia compared to higher doses of primaquine, highlighting the need to optimize tafenoquine dosing. Participants will be randomly assigned to receive either the current recommended tafenoquine dose or a 50% higher dose, both given as a single dose based on weight bands. An additional arm with high-dose primaquine is included only in Indonesia to compare with national treatment standards. All tafenoquine doses will be given with a schizonticidal agent, such as chloroquine or artemether-lumefantrine, with drug administration closely observed by study staff. Participants will be followed daily until malaria parasites clear, then at scheduled visits up to four months to monitor for recurrence and side effects. Study activities include blood tests, physical exams, vital signs, pregnancy and enzyme activity testing, and adverse event tracking. Data will be securely recorded and analyzed to compare treatment effectiveness and safety. Participants may withdraw at any time, and those with ongoing issues at study end will receive appropriate follow-up care.