Discontinuing atovaquone/proguanil prophylaxis ad-hoc post-exposure and during-travel dose-sparing prophylactic regimens against P. falciparum malaria: An update with pointers for future research

Background: Atovaquone/proguanil (AP) is a highly effective malaria chemoprophylaxis combination. According to current guidelines, AP is taken once daily during, and continued for seven days post exposure. A systematic review by Savelkoel et al. summarised data up to 2017 on abbreviated AP regimens, and concluded that discontinuing AP upon return may be effective, although the available data was insufficient to modify current recommendations. The same applies to other studies evaluating during-travel dose-sparing regimens. Methods: A literature search in Pubmed and Embase was performed including search terms related to AP prophylaxis and pharmacokinetics to search for recent studies on abbreviated AP regimens published since 2017. Results: Since the 2017 review, no new studies assessing discontinuing AP ad-hoc post-exposure prophylaxis have been published. Two new studies were identified assessing other abbreviated AP regimens; one investigated a twice-weekly AP regimen in 32 travellers, and one a three-day AP course in therapeutic dose (1000/400 mg) prior to exposure in 215 travellers. No malaria cases were detected in the study participants adhering to these regimens. Conclusions: Further research would be needed if the research question is considered of sufficient importance to facilitate evidence-based decision-making to modify current guidelines, as efficacy studies in travellers are fraught with confounders. We recommend human challenge trials to study abbreviated AP regimens pertaining to malaria chemoprophylaxis as they allow for rational, subject number, time- and cost-saving trial designs.