Artemether (INN) is an antimalarial for the treatment of multi-drug resistant strains of falciparum malaria. Its combination (co-formulation) with Lumefantrine has first been marketed by Novartis under the brand names Riamet and Coartem. Today, this combination therapy is available as generic from several manufacturers.
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Mechanisms of Action
The specific mechanism of action of artemisinin is not well understood, and there is ongoing research directed at elucidating it. When the parasite that causes malaria infects a red blood cell, it consumes hemoglobin and liberates free heme, an iron-porphyrin complex. The iron reduces the peroxide bond in artemisinin generating high-valent iron-oxo species, resulting in a cascade of reactions that produce reactive oxygen radicals which damage the parasite leading to its death.
Numerous studies have investigated the type of damage that these oxygen radicals may induce. For example, Pandey et al. have observed inhibition of digestive vacuole cysteine protease activity of malarial parasite by artemisinin. These observations were further confirmed by ex vivo experiments showing accumulation of hemoglobin in the parasites treated with artemisinin, suggesting inhibition of hemoglobin degradation. They found artemisinin to be a potent inhibitor of hemeozoin formation activity of malaria parasite.
A 2005 study investigating the mode of action of artemisinin using a yeast model demonstrated that the drug acts on the electron transport chain, generates local reactive oxygen species, and causes the depolarization of the mitochondrial membrane.
Artemisinins have also been shown to inhibit PfATP6, a SERCA-type enzyme (calcium transporter) and artemisinin has been shown to compete with thapsigargin for SERCA binding, though artemesinin is much less toxic to mammalian cells. Resistance to artemisinin is conferred by a single mutation in the calcium transporter (PfATP6). This mutation has been studied in the laboratory but recently a study from French Guiana in field isolates of malaria parasites has identified a different mutation in the calcium transporter (PfATP6) that is associated with resistance to artemether, lending support to the idea that PfATP6 is the target for artemisinins.
- Cumming, Jared N.; Ploypradith, Poonsakdi; Posner, Gary H.. Antimalarial activity of artemisinin (qinghaosu) and related trioxanes: mechanism(s) of action. Advances in Pharmacology (San Diego) (1997), 37 253-297.
- Pandey et al
- Li et al., PLOS Genetics, September 2005, Volume 1, Issue 3
- A.-C. Uhlemann et al. Nature Struct. Mol. Biol. 12, 628-629;2005