A new study published in the Malaria Journal has assessed the therapeutic response and safety of chloroquine and primaquine in patients with uncomplicated Plasmodium vivax malaria in the Amazonas Department of Colombia. The research, conducted in 2022, compared two primaquine regimens (7 vs. 14 days) when administered with chloroquine, both delivering a total primaquine dose of 210 mg. The study highlights the challenges of malaria treatment in remote areas and the importance of treatment supervision to ensure adherence and efficacy.
Background and Context
Plasmodium vivax malaria poses significant control challenges due to potential treatment failures and relapses originating from liver stages. Chloroquine, a first-line drug targeting the blood stage of the parasite, faces increasing resistance, particularly in South America. The 2022 Colombian clinical practice guidelines recommend chloroquine for 3 days combined with primaquine for 14 days (0.25 mg/kg/day), although a 7-day primaquine regimen (0.5 mg/kg/day) is sometimes used to improve adherence.
Study Design and Findings
The study evaluated patients with uncomplicated P. vivax malaria treated with chloroquine and either a 7-day or 14-day primaquine regimen. In cases where treatment was directly supervised by a medical team, both regimens achieved a 100% adequate therapeutic response. However, in unsupervised settings, therapeutic failures were observed in 10.5% and 5.0% of patients receiving the 7-day and 14-day primaquine courses, respectively. Overall, when combining supervised and unsupervised cases, the therapeutic efficacy reached 97%.
Implications of Supervised vs. Unsupervised Treatment
While the study could not definitively conclude the superiority of supervised treatment, the findings suggest that medical supervision and patient monitoring may reduce the likelihood of treatment failure. Factors such as reduced parasite susceptibility to chloroquine and inconsistent medication adherence in unsupervised groups may contribute to these failures. The co-administration of primaquine could have a synergistic effect on clearing asexual parasitaemia, potentially masking the impact of chloroquine resistance.
Comparison with Other Studies
Similar studies in other regions of Colombia, such as Chocó and Turbo, have reported high rates of adequate clinical and parasitological responses with supervised chloroquine and primaquine treatment. However, these findings contrast with studies in the Brazilian Amazon, where therapeutic failure rates have been reported despite combination therapy. A study in Afghanistan also indicated that recurrences were less common with chloroquine plus primaquine compared to chloroquine alone, even in unsupervised settings (hazard ratio 0.37, 95% CI 0.25–0.54).
Limitations and Future Directions
The study acknowledges several limitations, including selection biases due to nonrandomization and challenges in patient follow-up due to geographical barriers and patient mobility. Additionally, glucose-6-phosphate dehydrogenase (G6PD) testing was not conducted prior to treatment, as it is not standard practice in the region. The authors suggest that future controlled studies with longer follow-up periods and investigation of resistance markers could provide valuable insights into the efficacy and effectiveness of antimalarial treatments in the region.
