Short History of Chloroquine

For over forty years chloroquine (CQ), 4-aminoquinoline chloroquine, was the drug of choice for both preventing and treating malaria. CQ was effective and very economical and is still the only drug that can safely be used on children and pregnant women in their first trimester (mefloquine has been safely used on pregnant women in later trimesters). CQ had activity against all four of the malaria strains that infect humans: P.falciparum , P.vivax , P.malariae, P.ovale. Japanese control over natural sources of anti-malarials during the First World War spurred the research and discovery of synthetic anti-malarials and CQ has been manufactured and widley used since the late 1940s.

After only about ten to twelve years of use chloroquine resistance (CQR) in P. falciparum began appearing. Two initial foci of resistance developed simultaneously in Colombia and on the Cambodia-Thailand border. From these loci resistance spread throughout South America and southern Asia. By the late 1970s CQ resistance had reached Africa and has since spread across sub-Saharan Africa. Resistance is most likely due to parasite adaptation, improper use if medication by patient and CQ dosing at sub-therapeutic levels. Below are a maps of areas with CQR endemic strains. Sub-saharan Afica has the greatest incidence of infection as well as the most wide spread occurance of CQR.

NCID, 2002

CQ resistance in P. vivax has been found in South America and southern Asia; CQ resistance has not been reported in P. malariae or P. ovale. This is probably due to the lower prevalence of these strains. Because incidence of human infection by P. malariae and P. ovale is low the chance that these species would encounter CQ is also low, thus these species are not experencing any selctive pressure that could lead to the developement of CQR.

-- Main.lambje - 04 May 2005
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