Antihistamine could fight malaria, U.S. study shows

Last Updated: 2006-07-03 8:30:51 -0400 (Reuters Health)

WASHINGTON - An allergy drug pulled off the market in 1999 could work to treat malaria, U.S. researchers reported on Sunday.

The drug is called astemizole and marketed under the brand name Hismanal by Janssen Pharmaceutica, a unit of Johnson & Johnson, and can kill the Plasmodium falciparum parasite that causes malaria.

Researchers from the Johns Hopkins University Schools of Medicine and Public Health tested astemizole in test tubes and in mice. Moderate doses reduced the numbers of Plasmodium parasites by 80 percent in mice whose infection also could be affected by the malaria drug chloroquine.

In mice resistant to chloroquine, the antihistamine reduced parasite numbers by 40 percent, the researchers report in this week's issue of Nature Chemical Biology.

"Time and money are major roadblocks when it comes to developing new drugs for the treatment of neglected diseases like malaria," said Dr. David Sullivan, who oversaw the study.

"Astemizole is promising as an antimalarial, but still needs to be evaluated for effectiveness as an antimalarial in humans."

Malaria, caused by a single-cell parasite called Plasmodium that is carried by mosquitoes, kills at least a million people every year and makes 300 million people seriously ill.

The best treatment is with compounds known as artemisinins. They have been shown to reduce deaths from malaria by up to 30 percent if used properly and can cure falciparum malaria in seven days. In combination with other drugs they can do the job in three days.

Yet many countries still use older, much less effective drugs because the newer drugs are not available and are expensive.

For their study, Sullivan's team screened 2,687 known drugs for potential effectiveness in killing Plasmodium and found that astemizole was one of the more promising.

Janssen withdrew astemizole from the U.S. and European markets in 1999 after warnings about the drug's safety. It could cause rare, but life-threatening heart arrhythmias when patients took an overdose or with drugs that affected its metabolism.

But similar arrhythmias are reported with existing malaria drugs and other antihistamines now sold over the counter. Astemizole is still used in 30 countries, including Cambodia, Thailand and Vietnam where malaria is endemic, the researchers said.

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