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Study May Lead to New Tests for Liver Toxicity

Small fragments of genetic material in the blood may offer an early-warning sign that drugs are causing harm to the liver, U.S. researchers said on Monday.

Researchers at the Institute for Systems Biology, a research organization in Seattle, found that tiny bits of genetic material known microRNAs helped to accurately predict which mice had been given a toxic dose of the painkiller Tylenol, known generically as acetaminophen or paracetamol.

"It is a possibility that these microRNAs will be a very important biomarker not only for drug-induced liver injury, but for many different types of diseases," said Dr. Leroy Hood, whose study appears in the journal Proceedings of the National Academy of Sciences.

Liver toxicity is a common side effect of many drugs, Hood said. But doctors often lack a quick, easy blood test to detect toxicity before it causes serious harm.

"In this study, what we did was to look at normal animals and animals that were poisoned with acetaminophen," he said.

Next, they checked for levels of tiny bits of RNA in the blood that appeared in higher concentrations in the first 48 hours of acetaminophen poisoning.

"We found a relatively large number of microRNAs that changed in accordance with the liver toxicity," Hood said.

They found many of the microRNAs originated in the liver and made their way into the blood, suggesting they might be useful as a blood test.

Hood thinks the biomarkers might be useful as a way of testing whether a drug is causing harm to the liver.

"I think it could be used for any kind of drug-induced liver toxicity," he said.

Hood said he hopes the biomarkers eventually will become part of the process for all drugs undergoing safety screening while being considered for approval by the U.S. Food and Drug Administration.