Miami, United States—A cheap allergy drug that is taken for coughing, sneezing and runny nose may be useful in treating the chronic liver infection hepatitis C, US researchers said.

The antihistamine, called chlorcyclizine HCI, costs about 50 cents per pill, in sharp contrast to recent antiviral treatments that can cure hepatitis C for the first time, but at a hefty cost of at least $8,000 per four-month regimen.

Since some 185 million people worldwide suffer from hepatitis C, which can lead to cancer and cirrhosis of the liver, researchers said the new use for an old drug could offer hope for people particularly in Asia and Africa where the disease is endemic.

For the study, which appears in the journal Science Translational Medicine, researchers analyzed a library of drugs already approved by the US Food and Drug Administration to find candidates that might be useful for treating hepatitis C.

They found that chlorcyclizine HCI, which was approved about five decades ago, blocks hepatitis C infection by preventing the virus from entering human liver cells.

Research using lab mice that carried human liver cells showed that the drug could block the virus and did not lead to drug resistance, a common problem in hepatitis C treatments.

The drug also worked well with other hepatitis C drugs to make those treatments more effective.

Other FDA-approved drugs have previously been shown to be useful for clinical treatment of hepatitis C, including the anti-cancer drugs erlotinib and dasatinib; the cholesterol drug ezetimibe; and the anti-malaria treatment ferroquine.

However, the antihistamine showed even "more compelling in vitro and in vivo activity against HCV infection than these drugs," said the study, led by Shanshan He at the National Institutes of Health in Bethesda, Maryland.

Since the drug, also known as CCZ, has already been shown to be safe in humans, researchers called for clinical studies to see how it works against hepatitis C in people.

"With its established clinical safety profile as an allergy medication, affordability, and a simple chemical structure for optimization, CCZ represents a promising candidate for drug repurposing and further development as an effective and accessible agent for treatment of HCV infection," the study said.

"People should not take CCZ to treat their hepatitis C until it has been demonstrated that CCZ can be used safely and effectively for that purpose," said study author T. Jake Liang, senior investigator at NIH's National Institute of Diabetes and Digestive and Kidney Diseases.