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Second-string malaria drug can also prevent infection

NEW YORK (Reuters Health)-- Although not widely used to combat malaria, a

drug called atovaquone may help prevent the disease prior to exposure,

Baltimore researchers report in the September issue of the American Journal

of Tropical Medicine and Hygiene.

According to study lead author Dr. Theresa A. Shapiro, of s Hopkins

University in Baltimore, land, atovaquone proved 100% effective in

protecting persons bitten by malaria-carrying mosquitoes from developing the

disease.

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Malaria, transmitted by infected mosquitoes generally found in tropical and

subtropical countries, is characterized by fever, chills, headache, muscle

ache, and malaise. Contracting malaria can often be prevented by the use of

prescribed antimalarial drugs and vigilant use of bug spray.

In the current study, 12 volunteers received either a high or low dose of

atovaquone and 4 received (an inactive) placebo. Participants were bitten by

five mosquitoes infected with the Plasmodium falciparum parasite, which is

known to cause some of the most severe forms of the illness.

After 2 weeks, the individuals who received atovaquone showed no signs of

malarial infection. In contrast, the four subjects who had been given

placebo did develop malaria. Because daily blood tests were run on the

participants, the malarial infections were caught early and the patients

promptly placed on standard drug treatments. All recovered.

Current preventive drug therapy for malaria must be started before traveling

and is continued for weeks after returning home. " With atovaquone, " the

researchers explain in a press statement, " travelers should be able to take

their last dose as they leave (the malarial area). "

Calling this " a distinct advantage over the current suppressive regimen that

require 4 weeks of treatment after exposure, " Shapiro and colleagues write

that " this important practical consideration certainly merits confirmation

in larger trials with non-immune subjects exposed to an array of

(plasmodium) falciparum strains in various parts of the world. "

In an ancillary finding, the researchers noted that when atovaquone is used

in combination with an older antimalarial drug called proguanil, the dual

therapy may serve to prevent drug resistance from developing. The two work

at separate sites on the parasite, making it unlikely that a resistant

parasite could survive a two-pronged attack.

Atovaquone is a member of a drug class that dates back to World War II.

Because of toxicity and other problems associated with those early

forebears, other drugs were developed to combat malaria. In the 1970s,

atovaquone was synthesized and has lately come to be used to treat certain

infections associated with AIDS.

Source: American Journal of Tropical Medicine and Hygiene 1999;60:831-836.