Steps must be taken to avoid resistance to latest malaria drug, UN agency warns

6 September 2005

The United Nations health agency today called on countries to adopt monitoring measures to ensure that new life-saving malaria medicines do not lose their effectiveness through misuse, producing resistant strains of a disease that causes more than 300 million acute illnesses and 1 million deaths annually.

“It is crucial that these medicines be used correctly,” said Pascal Ringwald, a medical officer in the World Health Organization (WHO) Roll Back Malaria (RBM) Department and principal author of a new report on global monitoring of antimalarial drugs released today.

The report, "Susceptibility of Plasmodium falciparum to Antimalarial Drugs", warns that as more and more people gain access to the medicines, which combine a drug derived from the plant Artemisia annua with a second, synthetic drug, it is vital that countries closely monitor the drugs' effectiveness.

More than 50 governments have followed WHO’s recommendations on malaria treatment and adopted artemisinin-based combination therapies (ACTs), the most effective antimalarial drugs available today. This has enhanced prospects for reducing the burden of the disease worldwide.

Drugs derived from the plant Artemisia annua must be used as ACTs in combination with a second drug, and not alone. Otherwise, the medicines could lose their potency over time due to the development of resistance. This has already happened with other antimalarial drugs such as chloroquine, once a mainstay of treatment .

To avoid this, WHO is calling on countries to use only WHO-approved ACTs (an artemisinin-based drug combined with amodiaquine, lumefantrine, mefloquine or sulfadoxine–pyrimethamine) of high quality, since drugs of low potency can promote resistance.

All people taking antimalarials should be educated about the importance of finishing their course of medication, since incomplete treatment is another cause of resistance, WHO warned. Any change in efficacy of antimalarial drugs should prompt an appropriate update in a country’s treatment policy.

The danger of resistance stems from the malaria parasite’s ability to evade the lethal action of drugs. Because malaria parasites are genetically highly diverse, some strains can escape drugs unharmed and pass along their resistance to progeny. As sensitive organisms die off, resistant strains may come to dominate, and over time an antimalarial drug can lose its ability to cure infection.

Resistance is more likely to occur when only one drug is used. Combining an artemisinin-based medicine with another antimalarial drug, as WHO recommends, sharply reduces the risk. “To date no treatment failures due to artemisinin drug resistance have been documented, but we are watching the situation very attentively,” Dr. Ringwald said.

“We have the means to enhance the lifespan of ACTs. In addition, we must move forward energetically on research to develop new antimalarial medicines,” said Fatoumata Nafo-Traoré, Director of WHO’s RBM Department.

 

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