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Questions and Answers
What is the primary limitation of artemisinin as an antipyretic drug?
What is the mechanism of action of artemisinins against malaria parasites?
Why are artemisinins always combined with other antimalarial drugs?
What is a common characteristic of all artemisinins?
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Which of the following analogs of artemisinin is lipid-soluble?
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What is the primary role of artemisinins in the treatment of malaria?
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Which regimen is recommended for treating severe malaria in all stages of pregnancy in some countries?
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What is the primary reason for combining artemisinins with other drugs?
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Which of the following regimens is not co-formulated?
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In which trimester of pregnancy is a combination of quinine and clindamycin likely used?
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Study Notes
Artemisinin
- Artemisinin is the active component of a Chinese herbal medicine (artemisia annua) used as an antipyretic for over 2000 years.
- Artemisinin is hydrophobic, insoluble in water, and can only be administered orally.
Analogues of Artemisinin
- Dihydroartemisinin: more water-soluble, administered orally, and has improved antimalarial efficacy.
- Artesunate: water-soluble, administered through oral, IV, intramuscular, and rectal routes.
- Artemether: lipid-soluble, administered orally, intramuscularly, and rectally, due to its polarity.
Mechanism of Action
- Artemisinins have an endoperoxide bridge that produces free radicals when in contact with iron (Fe2+) in the Heme group.
- The free radicals neutralize malaria parasites through oxidative damage.
Chemotherapy
- Artemisinins are never used as a single drug, but are combined with other medications to reduce the risk of relapse.
- Combinations of artemisinins with other antimalarial drugs have a lower risk of relapse due to their short half-life.
Associations and Regimens
- Artemether-Lumefantrine (Coartem, Riamet): co-formulated, first-line therapy in many countries, approved in the USA.
- Artesunate-Amodiaquine (ASAQ, Arducam, Coarsucam): co-formulated, first-line therapy in many African countries.
- Artesunate-Mefloquine: co-formulated, first-line therapy in parts of Southeast Asia and South America.
- Dihydroartemisinin-Piperaquine (Artekin, Duocotexin): co-formulated, first-line therapy in some Southeast Asian countries.
- Artesunate-Sulfadoxine-Pyrimethamine: not co-formulated, first-line therapy in some countries, but less effective in most areas.
Pharmacokinetics
- All artemisinins have good absorption when given orally, and peak plasma levels are quickly reached.
- Artemisinin, artesunate, and artemether are quickly metabolized by CYP2A6 and CYp3A4/3A5, resulting in the synthesis of dihydroartemisinin.
- The half-lives of artemisinins are short (30-60 minutes for artesunate + dihydroartemisinin, and 2-3 hours for artemether).
Clinical Applications
- Artemisinins are effective for uncomplicated, complicated, and severe Plasmodium falciparum malaria infections.
- They are recommended for uncomplicated falciparum malaria during the 2nd and 3rd trimesters of pregnancy.
- In some countries, artesunate intravenously is recommended for treating severe malaria in all stages of pregnancy.
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Description
Learn about the chemical properties and uses of artemisinin, a traditional Chinese herbal medicine, and its analogues dihydroartemisinin, artesunate, and artemether.
