G6PD-guided primaquine reached community clinics with acceptable safety in vivax malaria
High-dose primaquine given after point-of-care glucose-6-phosphate dehydrogenase testing proved workable in routine community clinics across Papua New Guinea and Indonesia, with safety signals that fit the expected biology of oxidative hemolysis rather than an uncontrolled toxic pattern. Investigators enrolled 800 patients with Plasmodium vivax malaria and used the G6PD result to assign one of three radical cure regimens: 7 days of high-dose primaquine for those with normal G6PD activity, a 14-day regimen for intermediate activity, and an 8-week regimen for deficient patients.
The study asked a practical question that has dogged vivax malaria control for years: can radical cure be delivered safely where G6PD deficiency is common, lab infrastructure is limited, and adherence to a long treatment course is fragile? The answer from this multicenter field study was yes, at least under the conditions tested here. Point-of-care screening made treatment selection immediate, which matters because Plasmodium vivax relapse depends on dormant liver forms that keep seeding new episodes long after the initial fever clears.
Hemolysis was the main signal, but severe clinical harm did not emerge
A total of 27 adverse events of special interest were reported in 26 patients. Most were linked to hemolysis, and 21 events were defined by a hemoglobin fall greater than 3 g/dL. Even so, those drops occurred without clinical compromise, a crucial distinction in a setting where laboratory change and bedside instability are not always the same thing. In operational terms, the regimen triggered the biologic effect clinicians would watch for, yet it did not translate into the sort of decompensation that forces urgent intervention in this cohort.
The frequency of adverse events rose across the G6PD-stratified treatment groups: 2.7% among the 626 patients treated with PQ7, 4.1% among the 148 patients treated with PQ14, and 11.5% among the 26 patients treated with PQ8W. The smaller deficient group understandably deserves caution in interpretation, but the pattern is clinically coherent. Patients with enzyme deficiency remain more vulnerable to oxidant stress, and primaquine’s hemolytic potential tracks directly with that vulnerability.
Serious adverse events occurred in 16 patients, representing 2.0% of the total cohort. Most were gastrointestinal intolerance, accounting for 11 of 16 serious events, and they were concentrated in the PQ7 group. Among those who received PQ7, 9 of 626 patients, or 1.4%, had serious adverse events judged probably or possibly related to primaquine. The picture is not of a drug abandoned at the bedside, but of a regimen that requires the same practical attention to tolerability that any effective anti-relapse therapy would demand.
Adherence and follow-up remained high in the field
The operational details matter because they show what happened after the prescription left the clinic. Of the patients who did not withdraw, 97.8% were followed up on day 3 and 97.7% on day 7. In community malaria care, that level of follow-up is unusually important: early review is when hemolysis, nausea, and adherence problems are most likely to surface, and when a clinician can still intervene before a patient disappears back into the community.
This is where the shorter course has a plausible advantage beyond pharmacology. A 7-day regimen is easier to complete than a 14-day course, and both are far easier than an 8-week plan in most field settings. For vivax malaria, incomplete radical cure is not a minor inconvenience; it leaves the hypnozoite reservoir intact and keeps recurrence cycles alive. By pairing point-of-care G6PD testing with regimen selection, the study operationalized a treatment model that tries to match efficacy, safety, and adherence to the patient’s enzyme status.
Why the biology supports the strategy
Primaquine remains one of the few available drugs that can clear dormant liver stages of Plasmodium vivax. The problem has never been efficacy alone. Oxidative injury in red cells, especially among patients with G6PD deficiency, limits how aggressively clinicians can use it without testing. Point-of-care G6PD screening closes that gap by identifying who can safely receive the higher daily dose and who needs a modified schedule.
In this study, the screen-to-treatment pathway was simple enough to function in community clinics and robust enough to move 800 patients through enrollment and follow-up within a one-year window. The safety profile suggests that hemolysis can be anticipated, measured, and contained when treatment is guided by enzyme testing rather than delivered blindly. For malaria programs, that turns radical cure from a theoretical option into a deliverable intervention.
The public health value sits in implementation, not just efficacy
The trial does not claim that every patient can take the same regimen or that every health system can adopt it immediately. It does show that structured G6PD testing can direct primaquine use across three real-world dosing pathways with acceptable short-term safety. The practical consequence is important for endemic regions where repeated vivax infections sap school attendance, work capacity, and household stability.
The study also narrows the next question to implementation at scale: can health systems reproduce this level of safety and follow-up outside a tightly supervised study network? Funding from UNITAID and the Australian National Health and Medical Research Council helped build the evidence base, but broader adoption will depend on supply chains, staff training, diagnostic availability, and the ability to keep patients engaged after the first clinic visit.
The evidence here supports a cautious expansion of G6PD-guided primaquine use for radical cure in vivax malaria. What remains unresolved is how consistently the same safety profile will hold when the intervention moves from study clinics into the day-to-day demands of routine malaria care.