Antimalarial drug efficacy

Monitoring the efficacy of antimalarial medicines is a key component of malaria control. The consequences of resistance can be devastating. When chloroquine resistance spread across Africa in the 1980s, there was a dramatic rise in malaria-related deaths.

The steady appearance of Plasmodium falciparum resistance to many antimalarial medicines over the past several decades has since led malaria endemic countries to adopt artemisinin-based combination therapies (ACTs). Protecting the efficacy of ACTs as the current first-line treatment for P. falciparum malaria is now among the top global public health priorities.

Therapeutic efficacy studies

Therapeutic efficacy studies are prospective evaluations of patients’ clinical and parasitological responses to directly observed treatment for uncomplicated malaria. Studies at regular intervals at the same sites allow for the early detection of resistance. Findings also provide evidence for guiding national malaria treatment policy.

Therapeutic outcomes are assessed on the final day of the study (day 28, or day 42 for drugs with longer elimination half-lives). For infections appearing during follow-up, genotyping must be conducted to distinguish new infections from recrudescence.

WHO moreover recommends that:

  • National malaria control programmes adopt antimalarial medicines with a parasitological cure rate of more than 95%. Medicines should then be monitored at least once every 24 months at established sentinel sites.
  • A change in the national malaria treatment policy be initiated if the total treatment failure proportion is ≥ 10%, as assessed through in vivo monitoring of therapeutic efficacy.

Standardized procedures

These studies form part of a global surveillance system to monitor the emergence of antimalarial drug resistance. The use of standardized procedures facilitates the comparison of study results within and across regions over time. For this purpose, WHO has developed a standard protocol for monitoring therapeutic efficacy.

Protocols are also available for studies conducted to confirm and characterize drug resistance, including: in vitro studies of changes to the parasite phenotype, genotyping for determination of parasite recrudescence, and pharmacokinetic analyses of drug concentrations in blood.

WHO global antimalarial drug efficacy database

The database consolidates data collection on the status of antimalarial drug efficacy from malaria-endemic countries, effectively making up the largest collection of antimalarial drug efficacy studies ever reviewed and standardized for analysis.

Last updated: 25 March 2014

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