Antihistamine Can Kill Malaria Parasite, Could Be Used To Treat Disease, Study Says

The antihistamine astemizole can kill the Plasmodium falciparum malaria parasite and could be used to treat the disease, according to a study published in the July 2 online edition of Nature Chemical Biology, Reuters reports. The drug, which was sold in the U.S. under the brand name Hismanal by the Johnson & Johnson subsidiary Janssen Pharmaceutica, was taken off the U.S. market in 1999. Janssen withdrew astemizole in the U.S. and Europe after it was discovered that the drug could cause rare but potentially fatal heart arrhythmias when patients overdosed on the drug, or when it was taken with drugs that altered its metabolism. Similar arrhythmias can arise from existing malaria drugs and other nonprescription antihistamines, according to Reuters. For the study, David Sullivan, an associate professor at the Johns Hopkins Bloomberg School of Public Health, and colleagues screened 2,687 drugs to determine their effectiveness in killing P. falciparum and found astemizole to be one of the most effective (Reuters, 7/2). The researchers then administered the drug, along with the metabolite desmethylastemizol, to mice infected with the parasite. The researchers found that moderate doses of astemizole reduced parasite numbers by 80% in mice that were not resistant to chloroquine. In mice that were resistant to chloroquine, moderate doses of the drug reduced the parasite by 40%, the researchers found. High doses of the drug completely eliminated the parasite, according to the study. The researchers are planning to test the drug on asymptomatic malaria patients and hope to validate its use in combination with existing malaria drugs (JHSPH release, 6/2). Since the drug already is licensed for use in humans, it could be developed to treat malaria in about 12 months, according to the Guardian. In addition, because astemizole is no longer under patent, it could be produced at low costs (Randerson, Guardian, 7/3). The drug is still sold in 30 countries -- including Cambodia, Thailand and Vietnam -- the researchers said (Reuters, 7/2).